重刷leetcode-day6-[94. 二叉树的中序遍历]

【题目】 94. 二叉树的中序遍历

【题目考察】：二叉树、栈

【目标复杂度】： O(n)

【解法】：

/**
 * 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 cur = root;

    while(cur !== null || stack.length!== 0) {
        if (cur !== null) {
            stack.push(cur);
            cur = cur.left;
        } else {
            const top = stack.pop();
            res.push(top.val);
            cur = top.right;
        }
    }
    
    return res;
};