树操作-二叉树反转.js

  1. /**
  2.  * 二叉树--先序遍历
  3.  * @description
  4.  *  给定一个二叉树，{"val":1,"left":null,"right":{"val":2,"left":{"val":3,"left":null,"right":null},"right":null}}
  5.  *  使用先序遍历，返回output数组 [1, 2, 3]
  6.  * @param {Object}
  7.  * @returns {Array} 遍历后结果
  8.  */
  9. // Answer
  10. var preorderTraversal = function (root) {
  11.   var output = [];
  13.   var traversal = function (root) {
  14.     if (root.val) output.push(root.val);
  16.     if (root.left) traversal(root.left);
  18.     if (root.right) traversal(root.right);
  19.   };
  21.   traversal(root);
  23.   return output;
  24. };
  26. /**
  27.  * 二叉树反转
  28.  * @param {TreeNode} root
  29.  * @return {TreeNode}
  30.  */
  31. let root = {
  32.   val: 4,
  33.   left: {
  34.     val: 2,
  35.     left: {
  36.       val: 1,
  37.       left: null,
  38.       right: null,
  39.     },
  40.     right: {
  41.       val: 3,
  42.       left: null,
  43.       right: null,
  44.     },
  45.   },
  46.   right: {
  47.     val: 7,
  48.     left: {
  49.       val: 6,
  50.       left: null,
  51.       right: null,
  52.     },
  53.     right: {
  54.       val: 9,
  55.       left: null,
  56.       right: null,
  57.     },
  58.   },
  59. };
  61. var invertTree = function (root) {
  62.   if (!root) {
  63.     return root;
  64.   }
  66.   let val = root.right;
  67.   root.right = root.left;
  68.   root.left = val;
  70.   if (root.left) {
  71.     invertTree(root.left);
  72.   }
  74.   if (root.right) {
  75.     invertTree(root.right);
  76.   }
  78.   return root;
  79. };

栈操作-括号匹配.js

  1. // 判断字符串是否匹配
  2. let arr = '[][]()({{}}'

数组扁平化

  1. // 实现 Flat 函数，完成数组扁平化操作
  2. var arr = [1,2,3,[4,5,[6,7],8],2,2]
  4. nArr = []
  5. function fn(arr) {
  6.     arr.forEach(node => {
  7.         if(typeof node == 'number') {
  8.             nArr.push(node)
  9.         } else {
  10.             fn(node)
  11.         }
  12.     });
  13. }
  14. fn(arr)
  15. console.log(nArr);