103.二叉树的锯齿形层序遍历.ts

/*
 * @lc app=leetcode.cn id=103 lang=typescript
 *
 * [103] 二叉树的锯齿形层序遍历
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function zigzagLevelOrder(root: TreeNode | null): number[][] {
  if (!root) {
    return [];
  }

  const ans = [];
  const nodeQueue = [root];

  let isOrderLeft = true;

  while (nodeQueue.length) {
    let levelList = [];
    const size = nodeQueue.length;
    for (let i = 0; i < size; ++i) {
      const node = nodeQueue.shift()!;
      if (isOrderLeft) {
        levelList.push(node.val);
      } else {
        levelList.unshift(node.val);
      }
      node.left && nodeQueue.push(node.left);
      node.right && nodeQueue.push(node.right);
    }
    ans.push(levelList);
    isOrderLeft = !isOrderLeft;
  }

  return ans;
}
// @lc code=end