Online Judge►LeetCode

[LeetCode] 102 - Binary Tree Level Order Traversal

題意

Level Order Traversal 二元樹。

解法

BFS。

程式

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/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[][]}
 */
var levelOrder = function(root) {
  if ( !root ) return [];
  let queue = [root];
  let levels = [];
  while( queue.length !== 0 ){
    let length = queue.length;
    levels.push([]);
    for ( let i = 0; i < length; i ++ ){
      let node = queue.shift();
      levels[levels.length-1].push(node.val);
      if ( node.left ) queue.push(node.left);
      if ( node.right ) queue.push(node.right);
    }
  }
  return levels;
};