技術標籤：Leetcode演算法

Leetcode 103 二叉樹的鋸齒形層序遍歷

function TreeNode(val) {
    this.val = val;
    this.left = this.right = null;
};

var zigzagLevelOrder = function(root) {
    if (!root) {
        return [];
    }   
    return dfs(root);

    function dfs(root){
        const ans = []; //儲存返回結果
        const
 
 nodeQueue = [root]; //儲存二叉樹的結構，用於深搜的遍歷
        let isOrderLeft = true;  //決定遍歷的順序
        while (nodeQueue.length) { 
            let levelList = [];  //儲存同一深度上的節點值
            const size = nodeQueue.length; // 同一深度節點的個數
            for (let i = 0; i < size; ++i) {
                const node = nodeQueue.
 
shift();
                if (isOrderLeft) {
                    levelList.push(node.val);
                } else {
                    levelList.unshift(node.val);
                }
                if (node.left !== null) {
                    nodeQueue.push(node.left);
                }
                if
 
 (node.right !== null) {
                    nodeQueue.push(node.right);
                }
            }            
            ans.push(levelList);
            isOrderLeft = !isOrderLeft;
        }
        return ans;
    }
};