题目描述

原题链接

个人解法

Javascript

BFS

/*
 * @lc app=leetcode.cn id=102 lang=javascript
 *
 * [102] 二叉树的层序遍历
 */
// @lc code=start
/**
 * 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 levelOrder = function (root) {
  const result = [];
  if (root === null) {
    return [];
  }
  const myLevelOrder = function (roots) {
    const len = roots.length;
    if (len === 0) {
      return;
    } else {
      let temp = [];
      let nextRoots = [];
      for (let i = 0; i < len; i++) {
        temp.push(roots[i].val);
        roots[i].left && nextRoots.push(roots[i].left);
        roots[i].right && nextRoots.push(roots[i].right);
      }
      result.push(temp);
      myLevelOrder(nextRoots);
    }
  }
  myLevelOrder([root]);
  return result;
};
// @lc code=end

Java

其他解法

Java

Javascript

官方 BFS

题解链接

var levelOrder = function(root) {
    const ret = [];
    if (!root) {
        return ret;
    }
    const q = [];
    q.push(root);
    while (q.length !== 0) {
        const currentLevelSize = q.length;
        ret.push([]);
        for (let i = 1; i <= currentLevelSize; ++i) {
            const node = q.shift();
            ret[ret.length - 1].push(node.val);
            if (node.left) q.push(node.left);
            if (node.right) q.push(node.right);
        }
    }
    return ret;
};