Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).

For example:
Given binary tree {3,9,20,#,#,15,7},

    3
/ \
9 20
/ \
15 7

return its zigzag level order traversal as:

[
[3],
[20,9],
[15,7]
]

题目大意:给一个二叉树,将这个二叉树以zigzag形式输出,即一行以从左到右的顺序输出,下一行以从右到左的顺序输出……

解题思路:其实本质还是层次遍历,我们可以用cnt记录层数,奇数层从右到左,偶数层从左到右。用一个List记录这一层的数据,从左到右的顺序插入,从右到左的采用头插法插入即可。

Talk is cheap>>

    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> res = new ArrayList<>();
if (root == null) {
return res;
}
int cnt = 0;
Deque<TreeNode> queue = new ArrayDeque<>();
queue.offer(root);
while (!queue.isEmpty()) {
int size = queue.size();
List<Integer> level = new ArrayList<>();
for (int i = 0; i < size; i++) {
TreeNode node = queue.poll();
if ((cnt & 0x1) == 0) {
level.add(node.val);
} else {
level.add(0, node.val);
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
res.add(level);
cnt++;
}
return res;
}

Binary Tree Zigzag Level Order Traversal——LeetCode的更多相关文章

  1. Binary Tree Zigzag Level Order Traversal (LeetCode) 层序遍历二叉树

    题目描述: Binary Tree Zigzag Level Order Traversal AC Rate: 399/1474 My Submissions Given a binary tree, ...

  2. Binary Tree Zigzag Level Order Traversal [LeetCode]

    Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to ...

  3. Binary Tree ZigZag Level Order Traversal leetcode java

    题目: Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from lef ...

  4. 【LeetCode】 Binary Tree Zigzag Level Order Traversal 解题报告

    Binary Tree Zigzag Level Order Traversal [LeetCode] https://leetcode.com/problems/binary-tree-zigzag ...

  5. leetCode :103. Binary Tree Zigzag Level Order Traversal (swift) 二叉树Z字形层次遍历

    // 103. Binary Tree Zigzag Level Order Traversal // https://leetcode.com/problems/binary-tree-zigzag ...

  6. LeetCode 103. 二叉树的锯齿形层次遍历(Binary Tree Zigzag Level Order Traversal)

    103. 二叉树的锯齿形层次遍历 103. Binary Tree Zigzag Level Order Traversal 题目描述 给定一个二叉树,返回其节点值的锯齿形层次遍历.(即先从左往右,再 ...

  7. 【leetcode】Binary Tree Zigzag Level Order Traversal

    Binary Tree Zigzag Level Order Traversal Given a binary tree, return the zigzag level order traversa ...

  8. 【LeetCode】103. Binary Tree Zigzag Level Order Traversal

    Binary Tree Zigzag Level Order Traversal Given a binary tree, return the zigzag level order traversa ...

  9. [LeetCode] Binary Tree Level Order Traversal 与 Binary Tree Zigzag Level Order Traversal,两种按层次遍历树的方式,分别两个队列,两个栈实现

    Binary Tree Level Order Traversal Given a binary tree, return the level order traversal of its nodes ...

随机推荐

  1. poj 3565 ants

    /* poj 3565 递归分治 还有用KM的做法 这里写的分治 按紫书上的方法 不过那里说的有点冗杂了 可以简化一下 首先为啥可以分治 也就是分成子问题解决 只要有一个集合 黑白的个数相等 就一定能 ...

  2. Android TV 模拟器启动

    模拟器启动错误 使用IntelCPU的模拟器 http://software.intel.com/en-us/android/articles/intel-hardware-accelerated-e ...

  3. vs里 .sln和.suo 文件

    Net解决方案下 .sln文件和.suo文件的解释:When a Web site is created, a solution file (.sln) and a hidden solution u ...

  4. java_设计模式_工厂模式_Factory Pattern(2016-08-04)

    工厂模式主要是为创建对象提供了接口.工厂模式按照<Java与模式>中的提法分为三类: (1)简单工厂(Simple Factory)模式,又称静态工厂方法模式(Static Factory ...

  5. HDU 3359 Kind of a Blur(高斯消元)

    题意: H * W (W,H <= 10) 的矩阵A的某个元素A[i][j],从它出发到其他点的曼哈顿距离小于等于D的所有值的和S[i][j]除上可达点的数目,构成了矩阵B.给定矩阵B,求矩阵A ...

  6. 运用BeanUtils构建通用的查询 更新方法(个人拙作,不喜勿喷)

    ------------------------------------更新方法----------------------------------- public void update(Strin ...

  7. MVC埰坑日记 文件权限

    public static void DownLoadFile(string FileFullPath) { if (!string.IsNullOrEmpty(FileFullPath) & ...

  8. [转载]python os.path模块

    os.path模块主要用于文件的属性获取,在编程中经常用到,以下是该模块的几种常用方法.更多的方法可以去查看官方文档:http://docs.python.org/library/os.path.ht ...

  9. jquery的select元素和option的相关操作

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/ ...

  10. JqGrid自定义toolbar

    1.设置toolbar参数为[true,"top"],其意思是toolbar显示在Grid顶部,且其id为t_+Grid的id.e.g.: Grid的id为myGrid,toolb ...