94. 二叉树的中序遍历 about leetcode

[zzcyes]

题解

方法一：递归

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var preorderTraversal = function(root) {
  if (root == null) return [];
  const res = [];
  const recursive = (node) => {
    if (node == null) return;
    recursive(node.left);
    res.push(node.val);
    recursive(node.right);
  };
  recursive(root);
  return res;
};

方法二：迭代

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var inorderTraversal = function(root) {
   if(root == null) return [];
    let stack = [], res = [];
    let p = root;
    while(stack.length || p) {
        while(p) {
            stack.push(p);
            p = p.left;
        }
        let node = stack.pop();
        res.push(node.val);
        p = node.right;
    }
    return res;
};