exercise-book's Introduction

算法的练习本

leetcode每日一题

0826
0828

Java基本语法相关

栈和队列

初始化方式及API选择

      Stack<Integer> s = new Stack<>();
      
      LinkedList<Integer> s = new LinkedList<>(); //stack也可作为Linkedlist初始化
      
      Queue<PetEnterQueue> q = new LinkedList();

Stack类API:

      s.pop()
      s.push()
      s.peek()
      s.isempty()

LinkedList类的API:全

     s.add()
     s.addAll(Collection c)
     s.clear()
     s.contains()
     s.get(index)
     s.indexOf(Object o)

数组

遍历操作(也不是特别好用)

   for（int i : arr）{
   }

算法相关

计数排序及变形： https://www.runoob.com/w3cnote/counting-sort.html

Indexed Tree

Tree with pre and suf pointer. Inorder Traverse a tree by making it an indexed tree.

// non-iterative
public List<Integer> inorderTraversal(TreeNode root){
  List<Integer> res = new ArrayList<>();
  Deque<TreeNode> stack = new ArrayDeque<>();
  TreeNode cur = root;
  while(cur != null){
    if(cur.left == null){
      res.add(cur.val);
      cur = cur.right;
      }else{
        pre = cur.left;
      }
      pre.right = cur;
      TreeNode tmp = cur;
      cur = cur.left;
      tmp.left = null;
      }
   }
   return res;
}