# Binary Tree Zigzag Level Order Traversal LeetCode Solution

Here, We see Binary Tree Zigzag Level Order Traversal LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

# List of all LeetCode Solution

## Problem Statement

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

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: [[3],[20,9],[15,7]]

Example 2:
Input: root = [1]
Output: [[1]]

Example 3:
Input: root = []
Output: []

## Binary Tree Zigzag Level Order Traversal LeetCode SolutionC++

``````class Solution {
public:
vector<vector<int> > zigzagLevelOrder(TreeNode* root) {
if (root == NULL) {
return vector<vector<int> > ();
}
vector<vector<int> > result;
queue<TreeNode*> nodesQueue;
nodesQueue.push(root);
bool leftToRight = true;
while ( !nodesQueue.empty()) {
int size = nodesQueue.size();
vector<int> row(size);
for (int i = 0; i < size; i++) {
TreeNode* node = nodesQueue.front();
nodesQueue.pop();
int index = (leftToRight) ? i : (size - 1 - i);
row[index] = node->val;
if (node->left) {
nodesQueue.push(node->left);
}
if (node->right) {
nodesQueue.push(node->right);
}
}
leftToRight = !leftToRight;
result.push_back(row);
}
return result;
}
};```Code language: PHP (php)```

## Binary Tree Zigzag Level Order Traversal LeetCode SolutionJava

``````public class Solution {
public List<List<Integer>> zigzagLevelOrder(TreeNode root)
{
List<List<Integer>> sol = new ArrayList<>();
travel(root, sol, 0);
return sol;
}

private void travel(TreeNode curr, List<List<Integer>> sol, int level)
{
if(curr == null) return;
if(sol.size() <= level)
{
}
List<Integer> collection  = sol.get(level);
if(level % 2 == 0) collection.add(curr.val);
travel(curr.left, sol, level + 1);
travel(curr.right, sol, level + 1);
}
}```Code language: PHP (php)```

## Binary Tree Zigzag Level Order Traversal SolutionJavaScript

``````var zigzagLevelOrder = function(root) {
if(!root) return [];
let queue = [root];
let output = [];
let deep = 0;
while(queue.length > 0){
const size = queue.length;
const level = [];
for(let i=0; i< size; i++){
const node = queue.shift();
if(deep % 2 == 0) level.push(node.val);
else level.unshift(node.val);
if(node.left) queue.push(node.left)
if(node.right) queue.push(node.right)
}
output.push(level)
deep++;
}
return output
};```Code language: JavaScript (javascript)```

## Binary Tree Zigzag Level Order Traversal SolutionPython

``````class Solution(object):
def zigzagLevelOrder(self, root):
if not root: return []
queue = collections.deque([root])
res = []
even_level = False
while queue:
n = len(queue)
level = []
for _ in range(n):
node = queue.popleft()
level.append(node.val)
if node.left:
queue.append(node.left)
if node.right:
queue.append(node.right)
if even_level:
res.append(level[::-1])
else:
res.append(level)
even_level = not even_level
return res``````
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