Binary Tree Zigzag Level Order Traversal

class Solution {
public:
    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
        vector<vector<int>> ans;
        if (!root) return ans;
        queue<TreeNode*> q;
        q.push(root);
        bool leftToRight = true;
        while (!q.empty()) {
            int sz = q.size();
            vector<int> level(sz);
            for (int i = 0; i < sz; ++i) {
                TreeNode* cur = q.front(); q.pop();
                int idx = leftToRight ? i : sz - 1 - i;
                level[idx] = cur->val;
                if (cur->left) q.push(cur->left);
                if (cur->right) q.push(cur->right);
            }
            ans.push_back(std::move(level));
            leftToRight = !leftToRight;
        }
        return ans;
    }
};

func zigzagLevelOrder(root *TreeNode) [][]int {
    ans := [][]int{}
    if root == nil {
        return ans
    }
    queue := []*TreeNode{root}
    leftToRight := true
    for len(queue) > 0 {
        sz := len(queue)
        level := make([]int, sz)
        for i := 0; i < sz; i++ {
            cur := queue[0]
            queue = queue[1:]
            idx := i
            if !leftToRight {
                idx = sz - 1 - i
            }
            level[idx] = cur.Val
            if cur.Left != nil {
                queue = append(queue, cur.Left)
            }
            if cur.Right != nil {
                queue = append(queue, cur.Right)
            }
        }
        ans = append(ans, level)
        leftToRight = !leftToRight
    }
    return ans
}

from collections import deque
from typing import List, Optional

class Solution:
    def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
        ans: List[List[int]] = []
        if not root:
            return ans
        q = deque([root])
        left_to_right = True
        while q:
            sz = len(q)
            level = [0] * sz
            for i in range(sz):
                cur = q.popleft()
                idx = i if left_to_right else sz - 1 - i
                level[idx] = cur.val
                if cur.left:
                    q.append(cur.left)
                if cur.right:
                    q.append(cur.right)
            ans.append(level)
            left_to_right = not left_to_right
        return ans

var zigzagLevelOrder = function(root) {
    const ans = [];
    if (!root) return ans;
    const q = [root];
    let leftToRight = true;
    while (q.length > 0) {
        const sz = q.length;
        const level = new Array(sz);
        for (let i = 0; i < sz; i++) {
            const cur = q.shift();
            const idx = leftToRight ? i : sz - 1 - i;
            level[idx] = cur.val;
            if (cur.left) q.push(cur.left);
            if (cur.right) q.push(cur.right);
        }
        ans.push(level);
        leftToRight = !leftToRight;
    }
    return ans;
};

class Solution {
    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
        List<List<Integer>> ans = new ArrayList<>();
        if (root == null) return ans;
        Deque<TreeNode> q = new ArrayDeque<>();
        q.offer(root);
        boolean leftToRight = true;
        while (!q.isEmpty()) {
            int sz = q.size();
            Integer[] level = new Integer[sz];
            for (int i = 0; i < sz; i++) {
                TreeNode cur = q.poll();
                int idx = leftToRight ? i : sz - 1 - i;
                level[idx] = cur.val;
                if (cur.left != null) q.offer(cur.left);
                if (cur.right != null) q.offer(cur.right);
            }
            ans.add(Arrays.asList(level));
            leftToRight = !leftToRight;
        }
        return ans;
    }
}

function zigzagLevelOrder(root: TreeNode | null): number[][] {
    const ans: number[][] = [];
    if (!root) return ans;
    const q: TreeNode[] = [root];
    let leftToRight = true;
    while (q.length > 0) {
        const sz = q.length;
        const level: number[] = new Array(sz);
        for (let i = 0; i < sz; i++) {
            const cur = q.shift()!;
            const idx = leftToRight ? i : sz - 1 - i;
            level[idx] = cur.val;
            if (cur.left) q.push(cur.left);
            if (cur.right) q.push(cur.right);
        }
        ans.push(level);
        leftToRight = !leftToRight;
    }
    return ans;
}