알고리즘 실력 향상을 위해!!!
Task description
A string S consisting of N characters is considered to be properly nested if any of the following conditions is true:
S is empty; S has the form "(U)" or "[U]" or "{U}" where U is a properly nested string; S has the form "VW" where V and W are properly nested strings. For example, the string "{[()()]}" is properly nested but "([)()]" is not.
Write a function:
function solution(S);
that, given a string S consisting of N characters, returns 1 if S is properly nested and 0 otherwise.
For example, given S = "{[()()]}", the function should return 1 and given S = "([)()]", the function should return 0, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..200,000]; string S consists only of the following characters: "(", "{", "[", "]", "}" and/or ")".
// 3차 100% (닫는 괄호가 오는 경우 복사본으로 array.pop()하는 과정을 제거하였다.)
function solution(S) {
const array = []
const brackets = {
'(': ')',
'{': '}',
'[': ']'
}
for (let i = 0; i < S.length; i++) {
const openedBracket = brackets[S[i]]
if (openedBracket) {
array.push(S[i])
} else {
const lastedBracket = array.pop()
if (!lastedBracket || brackets[lastedBracket] !== S[i]) {
return 0
}
}
}
if (array.length) return 0
}
// 2차 75% (TIMEOUT ERROR)
function solution(S) {
if (S.length % 2) return 0
const array = []
const brackets = {
'(': ')',
'{': '}',
'[': ']'
}
for (let i = 0; i < S.length; i++) {
const openedBracket = brackets[S[i]]
if (openedBracket) {
array.push(S[i])
} else {
const lastedBracket = [...array].pop()
if (brackets[lastedBracket] === S[i]) {
array.pop()
} else {
return 0
}
}
}
if (array.length) return 0
return 1
}
// 1차 62% (TIMEOUT ERROR)
function solution(S) {
const array = []
const brackets = new Map([['(', ')'], ['{', '}'], ['[', ']']])
for (let i = 0; i < S.length; i++) {
if (brackets.get(S[i])) {
array.push(S[i])
} else {
const lastedBracket = [...array].pop()
if (brackets.get(lastedBracket) === S[i]) {
array.pop()
} else {
return 0
}
}
}
if (array.length) return 0
return 1
}Task description
We draw N discs on a plane. The discs are numbered from 0 to N − 1. An array A of N non-negative integers, specifying the radiuses of the discs, is given. The J-th disc is drawn with its center at (J, 0) and radius A[J].
We say that the J-th disc and K-th disc intersect if J ≠ K and the J-th and K-th discs have at least one common point (assuming that the discs contain their borders).
The figure below shows discs drawn for N = 6 and A as follows:
A[0] = 1 A[1] = 5 A[2] = 2 A[3] = 1 A[4] = 4 A[5] = 0
There are eleven (unordered) pairs of discs that intersect, namely:
discs 1 and 4 intersect, and both intersect with all the other discs; disc 2 also intersects with discs 0 and 3. Write a function:
function solution(A);
that, given an array A describing N discs as explained above, returns the number of (unordered) pairs of intersecting discs. The function should return −1 if the number of intersecting pairs exceeds 10,000,000.
Given array A shown above, the function should return 11, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..100,000]; each element of array A is an integer within the range [0..2,147,483,647].
// 1차 81% O(N**2) (TIMEOUT ERROR)
function solution(A) {
const result = A.reduce((sum, radius, index, origin) => {
let count = 0
const baseDisc = index + radius
for (let i = index + 1; i < origin.length; i++) {
const radius = origin[i]
const isIntersect = baseDisc >= i - radius
isIntersect && (count += 1)
}
return sum + count
}, 0)
return result
}Task description
An array A consisting of N integers is given. A triplet (P, Q, R) is triangular if 0 ≤ P < Q < R < N and:
A[P] + A[Q] > A[R], A[Q] + A[R] > A[P], A[R] + A[P] > A[Q]. For example, consider array A such that:
A[0] = 10 A[1] = 2 A[2] = 5 A[3] = 1 A[4] = 8 A[5] = 20 Triplet (0, 2, 4) is triangular.
Write a function:
function solution(A);
that, given an array A consisting of N integers, returns 1 if there exists a triangular triplet for this array and returns 0 otherwise.
For example, given array A such that:
A[0] = 10 A[1] = 2 A[2] = 5 A[3] = 1 A[4] = 8 A[5] = 20 the function should return 1, as explained above. Given array A such that:
A[0] = 10 A[1] = 50 A[2] = 5 A[3] = 1 the function should return 0.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..100,000]; each element of array A is an integer within the range [−2,147,483,648..2,147,483,647].
// 1차 100% O(N*log(N))
// (순서대로 정렬 후 인접한 세 수에서 작은 두 수의 합이 가장 큰 수를 초과하는지 확인하면 된다. 2 이상의 수가 3개가 안되면 조건을 충족할 수 없으므로 early 리턴 처리했다.)
function solution(A) {
const sortedNumbers = A.filter(number => number > 1).sort((a, b) => b - a)
if (sortedNumbers.length < 3) return 0
for (let i = 0; i < sortedNumbers.length; i++) {
if (sortedNumbers[i] < sortedNumbers[i + 1] + sortedNumbers[i + 2]) return 1
}
return 0
}Task description
A non-empty array A consisting of N integers is given. The product of triplet (P, Q, R) equates to A[P] * A[Q] * A[R] (0 ≤ P < Q < R < N).
For example, array A such that:
A[0] = -3 A[1] = 1 A[2] = 2 A[3] = -2 A[4] = 5 A[5] = 6 contains the following example triplets:
(0, 1, 2), product is −3 * 1 * 2 = −6 (1, 2, 4), product is 1 * 2 * 5 = 10 (2, 4, 5), product is 2 * 5 * 6 = 60 Your goal is to find the maximal product of any triplet.
Write a function:
function solution(A);
that, given a non-empty array A, returns the value of the maximal product of any triplet.
For example, given array A such that:
A[0] = -3 A[1] = 1 A[2] = 2 A[3] = -2 A[4] = 5 A[5] = 6 the function should return 60, as the product of triplet (2, 4, 5) is maximal.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [3..100,000]; each element of array A is an integer within the range [−1,000..1,000].
// 3차 100% O(N * log(N))
// (가장 큰 3수의 곱, 그리고 가장 작은 2수의 곱 * 가장 큰 수를 비교하면 되는 것이었다. 어쩐지 난이도가 Easy로 표기되어 있더라니...)
function multiply(array = []) {
return array.reduce((multiplied, number) => multiplied * number, 1)
}
function solution(A) {
const sortedNumbers = [...A].sort((a, b) => b - a)
const result = Math.max(multiply(sortedNumbers.slice(0, 3)), multiply([sortedNumbers[0], ...sortedNumbers.slice(-2)]))
return result
}
// 2차 88% 1개 오답(예상치 못한 경우 오답 발생, [4, 7, 3, 2, 1, -3, -5])
function multifly(array = []) {
return array.reduce((multiflied, number) => multiflied * number, 1)
}
function solution(A) {
const isNegativeOnly = A.every(number => number < 0)
const sortedNumbers = [...A].sort((a, b) => b - a)
const multiflied = {
positive: sortedNumbers.slice(0, 2),
negative: sortedNumbers.slice(-2)
}
const big3 = multifly(multiflied.positive) > multifly(multiflied.negative) || isNegativeOnly
? sortedNumbers.slice(0, 3)
: [sortedNumbers[0], ...multiflied.negative]
return multifly(big3)
}
// 1차 77% 2개 오답(음수만 있는 경우 오답 발생)
function multifly(array = []) {
return array.reduce((multiflied, number) => multiflied * number, 1)
}
function solution(A) {
const isNegativeOnly = A.every(number => number < 0)
const sortedNumbers = [...A].sort((a, b) => b - a)
const multiflied = {
positive: sortedNumbers.slice(0, 2),
negative: sortedNumbers.slice(-2)
}
const big3 = multifly(multiflied.positive) > multifly(multiflied.negative) || isNegativeOnly
? sortedNumbers.slice(0, 3)
: [sortedNumbers[0], ...multiflied.negative]
return multifly(big3)
}Task description
that, given an array A consisting of N integers, returns the number of distinct values in array A.
For example, given array A consisting of six elements such that:
A[0] = 2 A[1] = 1 A[2] = 1 A[3] = 2 A[4] = 3 A[5] = 1 the function should return 3, because there are 3 distinct values appearing in array A, namely 1, 2 and 3.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..100,000]; each element of array A is an integer within the range [−1,000,000..1,000,000].
// 1차 100% O(N*log(N)) or O(N)
function solution(A) {
return new Set(A).size
}Task description
A non-empty array A consisting of N integers is given. A pair of integers (P, Q), such that 0 ≤ P < Q < N, is called a slice of array A (notice that the slice contains at least two elements). The average of a slice (P, Q) is the sum of A[P] + A[P + 1] + ... + A[Q] divided by the length of the slice. To be precise, the average equals (A[P] + A[P + 1] + ... + A[Q]) / (Q − P + 1).
For example, array A such that:
A[0] = 4
A[1] = 2
A[2] = 2
A[3] = 5
A[4] = 1
A[5] = 5
A[6] = 8
contains the following example slices:
slice (1, 2), whose average is (2 + 2) / 2 = 2; slice (3, 4), whose average is (5 + 1) / 2 = 3; slice (1, 4), whose average is (2 + 2 + 5 + 1) / 4 = 2.5. The goal is to find the starting position of a slice whose average is minimal.
Write a function:
function solution(A);
that, given a non-empty array A consisting of N integers, returns the starting position of the slice with the minimal average. If there is more than one slice with a minimal average, you should return the smallest starting position of such a slice.
For example, given array A such that:
A[0] = 4
A[1] = 2
A[2] = 2
A[3] = 5
A[4] = 1
A[5] = 5
A[6] = 8
the function should return 1, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [2..100,000]; each element of array A is an integer within the range [−10,000..10,000].
// 1차 70% (Correctness: 60%, Performance 80%)
function solution(A) {
const results = {
index: null,
average: null
}
A.forEach((num, index) => {
const average = num + A[index + 1] / 2
if (typeof results.index !== 'number') {
results.index = index
results.average = average
return
}
if (results.average > average) {
results.index = index
results.average = average
}
})
return results.index
}
// 2차 100% O(N)
// 두 수 또는 세 수의 평균만 확인하면 된다는 수학적 공식을 알고 있어야 풀 수 있는 문제였다. 이를 힌트삼아 작성해 보았다.
function toAverage(array = []) {
return array.reduce((sum, number) => sum + number) / array.length
}
function solution(A) {
const minimum = {
starting: null,
average: null
}
for (let index = 0; index < A.length - 1; index++) {
const average = Math.min(toAverage(A.slice(index, index + 2)), toAverage(A.slice(index, index + 3)))
if (typeof minimum.starting === 'number') {
minimum.average > average &&
(minimum.starting = index, minimum.average = average)
} else {
minimum.starting = index
minimum.average = average
}
}
return minimum.starting
}Task description
A DNA sequence can be represented as a string consisting of the letters A, C, G and T, which correspond to the types of successive nucleotides in the sequence. Each nucleotide has an impact factor, which is an integer. Nucleotides of types A, C, G and T have impact factors of 1, 2, 3 and 4, respectively. You are going to answer several queries of the form: What is the minimal impact factor of nucleotides contained in a particular part of the given DNA sequence?
The DNA sequence is given as a non-empty string S = S[0]S[1]...S[N-1] consisting of N characters. There are M queries, which are given in non-empty arrays P and Q, each consisting of M integers. The K-th query (0 ≤ K < M) requires you to find the minimal impact factor of nucleotides contained in the DNA sequence between positions P[K] and Q[K] (inclusive).
For example, consider string S = CAGCCTA and arrays P, Q such that:
P[0] = 2 Q[0] = 4
P[1] = 5 Q[1] = 5
P[2] = 0 Q[2] = 6
The answers to these M = 3 queries are as follows:
The part of the DNA between positions 2 and 4 contains nucleotides G and C (twice), whose impact factors are 3 and 2 respectively, so the answer is 2. The part between positions 5 and 5 contains a single nucleotide T, whose impact factor is 4, so the answer is 4. The part between positions 0 and 6 (the whole string) contains all nucleotides, in particular nucleotide A whose impact factor is 1, so the answer is 1. Write a function:
function solution(S, P, Q);
that, given a non-empty string S consisting of N characters and two non-empty arrays P and Q consisting of M integers, returns an array consisting of M integers specifying the consecutive answers to all queries.
Result array should be returned as an array of integers.
For example, given the string S = CAGCCTA and arrays P, Q such that:
P[0] = 2 Q[0] = 4
P[1] = 5 Q[1] = 5
P[2] = 0 Q[2] = 6
the function should return the values [2, 4, 1], as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..100,000]; M is an integer within the range [1..50,000]; each element of arrays P and Q is an integer within the range [0..N − 1]; P[K] ≤ Q[K], where 0 ≤ K < M; string S consists only of upper-case English letters A, C, G, T.
// 1차 62% O(N * M)
function solution(S, P, Q) {
const letters = {
A: 1,
C: 2,
G: 3,
T: 4
}
const results = P.map((start, index) => {
const [letter] = [...new Set(S.slice(start, Q[index] + 1))].sort()
return letters[letter]
})
return results
}
// 2차 100% O(N + M)
function solution(S, P, Q) {
const results = []
P.forEach((start, index) => {
const range = S.slice(start, Q[index] + 1)
if (range.includes('A')) return results.push(1)
if (range.includes('C')) return results.push(2)
if (range.includes('G')) return results.push(3)
if (range.includes('T')) return results.push(4)
})
return results
}Task description
Write a function:
function solution(A, B, K);
that, given three integers A, B and K, returns the number of integers within the range [A..B] that are divisible by K, i.e.:
{ i : A ≤ i ≤ B, i mod K = 0 }
For example, for A = 6, B = 11 and K = 2, your function should return 3, because there are three numbers divisible by 2 within the range [6..11], namely 6, 8 and 10.
Write an efficient algorithm for the following assumptions:
A and B are integers within the range [0..2,000,000,000]; K is an integer within the range [1..2,000,000,000]; A ≤ B.
function solution(A, B, K) {
return Math.floor(B / K) - Math.ceil(A / K) + 1
}Task description
A non-empty array A consisting of N integers is given. The consecutive elements of array A represent consecutive cars on a road.
Array A contains only 0s and/or 1s:
0 represents a car traveling east, 1 represents a car traveling west. The goal is to count passing cars. We say that a pair of cars (P, Q), where 0 ≤ P < Q < N, is passing when P is traveling to the east and Q is traveling to the west.
For example, consider array A such that:
A[0] = 0 A[1] = 1 A[2] = 0 A[3] = 1 A[4] = 1 We have five pairs of passing cars: (0, 1), (0, 3), (0, 4), (2, 3), (2, 4).
Write a function:
function solution(A);
that, given a non-empty array A of N integers, returns the number of pairs of passing cars.
The function should return −1 if the number of pairs of passing cars exceeds 1,000,000,000.
For example, given:
A[0] = 0 A[1] = 1 A[2] = 0 A[3] = 1 A[4] = 1 the function should return 5, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..100,000]; each element of array A is an integer that can have one of the following values: 0, 1.
문제 해석이 잘 되지 않음...
Task description
This is a demo task.
Write a function:
function solution(A);
that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.
For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.
Given A = [1, 2, 3], the function should return 4.
Given A = [−1, −3], the function should return 1.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..100,000]; each element of array A is an integer within the range [−1,000,000..1,000,000].
function solution(A) {
const sortedNumbers = [...new Set(A)]
.filter(number => number > 0)
.sort((a, b) => a - b)
const [firstNumber] = sortedNumbers
const lastNumber = [...sortedNumbers].pop()
if (firstNumber !== 1) return 1
if (lastNumber === sortedNumbers.length) return lastNumber + 1
for (let i = 0; i < sortedNumbers.length; i++) {
if (sortedNumbers[i] !== i + 1) return i + 1
}
}Task description
You are given N counters, initially set to 0, and you have two possible operations on them:
increase(X) − counter X is increased by 1, max counter − all counters are set to the maximum value of any counter. A non-empty array A of M integers is given. This array represents consecutive operations:
if A[K] = X, such that 1 ≤ X ≤ N, then operation K is increase(X), if A[K] = N + 1 then operation K is max counter. For example, given integer N = 5 and array A such that:
A[0] = 3
A[1] = 4
A[2] = 4
A[3] = 6
A[4] = 1
A[5] = 4
A[6] = 4
the values of the counters after each consecutive operation will be:
(0, 0, 1, 0, 0)
(0, 0, 1, 1, 0)
(0, 0, 1, 2, 0)
(2, 2, 2, 2, 2)
(3, 2, 2, 2, 2)
(3, 2, 2, 3, 2)
(3, 2, 2, 4, 2)
The goal is to calculate the value of every counter after all operations.
Write a function:
function solution(N, A);
that, given an integer N and a non-empty array A consisting of M integers, returns a sequence of integers representing the values of the counters.
Result array should be returned as an array of integers.
For example, given:
A[0] = 3
A[1] = 4
A[2] = 4
A[3] = 6
A[4] = 1
A[5] = 4
A[6] = 4
the function should return [3, 2, 2, 4, 2], as explained above.
Write an efficient algorithm for the following assumptions:
N and M are integers within the range [1..100,000]; each element of array A is an integer within the range [1..N + 1].
function solution(N, A) {
const counters = [...new Array(N)].fill(0)
let maxCounter = 0
let runnedMaxCounter = 0
A.forEach(x => {
const idx = x - 1
if (x <= N) {
counters[idx] = Math.max(counters[idx], runnedMaxCounter) + 1
maxCounter = Math.max(counters[idx], maxCounter)
} else {
runnedMaxCounter = maxCounter
}
})
const result = counters.map(counter => {
return Math.max(counter, runnedMaxCounter)
})
return result
}Task description
A non-empty array A consisting of N integers is given.
A permutation is a sequence containing each element from 1 to N once, and only once.
For example, array A such that:
A[0] = 4
A[1] = 1
A[2] = 3
A[3] = 2
is a permutation, but array A such that:
A[0] = 4
A[1] = 1
A[2] = 3
is not a permutation, because value 2 is missing.
The goal is to check whether array A is a permutation.
Write a function:
function solution(A);
that, given an array A, returns 1 if array A is a permutation and 0 if it is not.
For example, given array A such that:
A[0] = 4
A[1] = 1
A[2] = 3
A[3] = 2
the function should return 1.
Given array A such that:
A[0] = 4
A[1] = 1
A[2] = 3
the function should return 0.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..100,000]; each element of array A is an integer within the range [1..1,000,000,000].
function solution(A) {
const set = new Set(A)
if (set.size !== A.length) return 0
return Math.max(...A) === A.length ? 1 : 0
}Task description
A small frog wants to get to the other side of a river. The frog is initially located on one bank of the river (position 0) and wants to get to the opposite bank (position X+1). Leaves fall from a tree onto the surface of the river.
You are given an array A consisting of N integers representing the falling leaves. A[K] represents the position where one leaf falls at time K, measured in seconds.
The goal is to find the earliest time when the frog can jump to the other side of the river. The frog can cross only when leaves appear at every position across the river from 1 to X (that is, we want to find the earliest moment when all the positions from 1 to X are covered by leaves). You may assume that the speed of the current in the river is negligibly small, i.e. the leaves do not change their positions once they fall in the river.
For example, you are given integer X = 5 and array A such that:
A[0] = 1 A[1] = 3 A[2] = 1 A[3] = 4 A[4] = 2 A[5] = 3 A[6] = 5 A[7] = 4 In second 6, a leaf falls into position 5. This is the earliest time when leaves appear in every position across the river.
Write a function:
function solution(X, A);
that, given a non-empty array A consisting of N integers and integer X, returns the earliest time when the frog can jump to the other side of the river.
If the frog is never able to jump to the other side of the river, the function should return −1.
For example, given X = 5 and array A such that:
A[0] = 1 A[1] = 3 A[2] = 1 A[3] = 4 A[4] = 2 A[5] = 3 A[6] = 5 A[7] = 4 the function should return 6, as explained above.
Write an efficient algorithm for the following assumptions:
N and X are integers within the range [1..100,000]; each element of array A is an integer within the range [1..X].
function solution(X, A) {
const set = new Set()
for (let i = 0; i < A.length; i++) {
set.add(A[i])
if (set.size === X) return i
}
return -1
}Task description
A non-empty array A consisting of N integers is given. Array A represents numbers on a tape.
Any integer P, such that 0 < P < N, splits this tape into two non-empty parts: A[0], A[1], ..., A[P − 1] and A[P], A[P + 1], ..., A[N − 1].
The difference between the two parts is the value of: |(A[0] + A[1] + ... + A[P − 1]) − (A[P] + A[P + 1] + ... + A[N − 1])|
In other words, it is the absolute difference between the sum of the first part and the sum of the second part.
For example, consider array A such that:
A[0] = 3
A[1] = 1
A[2] = 2
A[3] = 4
A[4] = 3
We can split this tape in four places:
P = 1, difference = |3 − 10| = 7 P = 2, difference = |4 − 9| = 5 P = 3, difference = |6 − 7| = 1 P = 4, difference = |10 − 3| = 7 Write a function:
function solution(A);
that, given a non-empty array A of N integers, returns the minimal difference that can be achieved.
For example, given:
A[0] = 3
A[1] = 1
A[2] = 2
A[3] = 4
A[4] = 3
the function should return 1, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [2..100,000]; each element of array A is an integer within the range [−1,000..1,000].
function solution(A) {
const sumParts = {
first: 0,
second: 0,
total: A.reduce((sum, number) => sum + number, 0)
}
let { first, second, total } = sumParts
const results = []
for (i = 0; i < A.length - 1; i++) {
first += A[i]
second = total - first
results.push(Math.abs(first - second))
}
return Math.min(...results)
}Task description
An array A consisting of N different integers is given. The array contains integers in the range [1..(N + 1)], which means that exactly one element is missing.
Your goal is to find that missing element.
Write a function:
function solution(A);
that, given an array A, returns the value of the missing element.
For example, given array A such that:
A[0] = 2
A[1] = 3
A[2] = 1
A[3] = 5
the function should return 4, as it is the missing element.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..100,000]; the elements of A are all distinct; each element of array A is an integer within the range [1..(N + 1)].
function solution(A) {
const ONE = 1
if (!A.length) return ONE
const sortedNumbers = [...A].sort((a, b) => a - b)
const [firstNumber] = sortedNumbers
if (firstNumber !== ONE) return ONE
const result = sortedNumbers.find((num, index, origin) => {
return !((num + origin[index + 1]) % 2)
})
return result + 1
}Task description
A small frog wants to get to the other side of the road. The frog is currently located at position X and wants to get to a position greater than or equal to Y. The small frog always jumps a fixed distance, D.
Count the minimal number of jumps that the small frog must perform to reach its target.
Write a function:
function solution(X, Y, D);
that, given three integers X, Y and D, returns the minimal number of jumps from position X to a position equal to or greater than Y.
For example, given:
X = 10
Y = 85
D = 30
the function should return 3, because the frog will be positioned as follows:
after the first jump, at position 10 + 30 = 40 after the second jump, at position 10 + 30 + 30 = 70 after the third jump, at position 10 + 30 + 30 + 30 = 100 Write an efficient algorithm for the following assumptions:
X, Y and D are integers within the range [1..1,000,000,000]; X ≤ Y.
function solution(X, Y, D) {
return Math.ceil((Y - X) / D)
}Task description
A non-empty array A consisting of N integers is given. The array contains an odd number of elements, and each element of the array can be paired with another element that has the same value, except for one element that is left unpaired.
For example, in array A such that:
A[0] = 9 A[1] = 3 A[2] = 9
A[3] = 3 A[4] = 9 A[5] = 7
A[6] = 9
the elements at indexes 0 and 2 have value 9, the elements at indexes 1 and 3 have value 3, the elements at indexes 4 and 6 have value 9, the element at index 5 has value 7 and is unpaired. Write a function:
function solution(A);
that, given an array A consisting of N integers fulfilling the above conditions, returns the value of the unpaired element.
For example, given array A such that:
A[0] = 9 A[1] = 3 A[2] = 9
A[3] = 3 A[4] = 9 A[5] = 7
A[6] = 9
the function should return 7, as explained in the example above.
Write an efficient algorithm for the following assumptions:
N is an odd integer within the range [1..1,000,000]; each element of array A is an integer within the range [1..1,000,000,000]; all but one of the values in A occur an even number of times.
function solution(A) {
const counters = A.reduce((counter, num) => {
counter[num] = counter[num] ? counter[num] + 1 : 1
return counter
}, {})
for (const key in counters) {
if (counters[key] % 2) return +key;
}
}Task description
An array A consisting of N integers is given. Rotation of the array means that each element is shifted right by one index, and the last element of the array is moved to the first place. For example, the rotation of array A = [3, 8, 9, 7, 6] is [6, 3, 8, 9, 7] (elements are shifted right by one index and 6 is moved to the first place).
The goal is to rotate array A K times; that is, each element of A will be shifted to the right K times.
Write a function:
function solution(A, K);
that, given an array A consisting of N integers and an integer K, returns the array A rotated K times.
For example, given
A = [3, 8, 9, 7, 6]
K = 3
the function should return [9, 7, 6, 3, 8]. Three rotations were made:
[3, 8, 9, 7, 6] -> [6, 3, 8, 9, 7]
[6, 3, 8, 9, 7] -> [7, 6, 3, 8, 9]
[7, 6, 3, 8, 9] -> [9, 7, 6, 3, 8]
For another example, given
A = [0, 0, 0]
K = 1
the function should return [0, 0, 0]
Given
A = [1, 2, 3, 4]
K = 4
the function should return [1, 2, 3, 4]
Assume that:
N and K are integers within the range [0..100]; each element of array A is an integer within the range [−1,000..1,000]. In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.
function solution(A, K) {
const moves = K % A.length
if (!moves || new Set(A).size === 1) return A
return [...A.slice(-1 * moves), ...A.slice(0, A.length - moves)]
}Task description
A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ends in the binary representation of N.
For example, number 9 has binary representation 1001 and contains a binary gap of length 2. The number 529 has binary representation 1000010001 and contains two binary gaps: one of length 4 and one of length 3. The number 20 has binary representation 10100 and contains one binary gap of length 1. The number 15 has binary representation 1111 and has no binary gaps. The number 32 has binary representation 100000 and has no binary gaps.
Write a function:
function solution(N);
that, given a positive integer N, returns the length of its longest binary gap. The function should return 0 if N doesn't contain a binary gap.
For example, given N = 1041 the function should return 5, because N has binary representation 10000010001 and so its longest binary gap is of length 5. Given N = 32 the function should return 0, because N has binary representation '100000' and thus no binary gaps.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..2,147,483,647].
function solution(N) {
const binary = N.toString(2)
const validGaps = binary
.split('1')
.slice(1, -1)
if (!validGaps.length) return validGaps.length
const gaps = validGaps.map(gap => gap.length)
return Math.max(...gaps)
}
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