94. 二叉树的中序遍历

[qulingyuan]

94. 二叉树的中序遍历

递归版：

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var inorderTraversal = function(root) {
    const res = [];
    const inorder = (n)=>{
        if(!n) return;
        inorder(n.left);
        res.push(n.val);
        inorder(n.right);
    }
    inorder(root);
    return res;
};

迭代版

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var inorderTraversal = function(root) {
    const res = [];
    const stack = [];
    let p = root;
    while(stack.length || p){
        while(p){
        stack.push(p);
        p = p.left;
    }
        const n = stack.pop();
        res.push(n.val);
        p = n.right;
    }
    return res;
};