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Merged
merged 2 commits into from
Oct 18, 2024
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Create 0103-binary-tree-zigzag-level-order-traversal.js #3588

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79fd29b
Create 0103-binary-tree-zigzag-level-order-traversal.js
aadil42 Aug 5, 2024
81d45a1
Update 0103-binary-tree-zigzag-level-order-traversal.js
aadil42 Oct 18, 2024
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49 changes: 49 additions & 0 deletions javascript/0103-binary-tree-zigzag-level-order-traversal.js
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/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* BFS | LevelOrderTraversal
* Time O(n) | Space O(n)
* https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
* @param {TreeNode} root
* @return {number[][]}
*/
var zigzagLevelOrder = function(root) {

const q = new Queue();

if(root) q.enqueue(root);

let isLeft = true;
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Can use better names

/**
 * BFS
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
 * @param {TreeNode} root
 * @return {number[][]}
 */
var zigzagLevelOrder = (root) => {
    const isEdgeBase = (root === null);
    if (isEdgeBase) return [];
    
    return search(root);/* Time O(N) | Space O(N) */
};

var search = (root, isZigZag = true, order = []) => {
    const queue = new Queue([ root ]);
    
    while (!queue.isEmpty()) {        /* Time O(N) */
        const levels = [];

        bfs(queue, isZigZag, levels); /* Time O(WIDTH) | Space O(WIDTH) */
        order.push(levels);           /*                 Space O(N) */
        isZigZag = !isZigZag;
    }
    
    return order;
}

const bfs = (queue, isZigZag, levels) => {
    for (let level = queue.size(); (0 < level); level--) {/* Time O(WIDTH) */
        const { left, val, right } = queue.dequeue();
    
        if (left) queue.enqueue(left);  /* Space O(WIDTH) */
        if (right) queue.enqueue(right);/* Space O(WIDTH) */
        
        levels.push(val);               /* Space O(N) */
    }

    if (!isZigZag) levels.reverse();
}

/**
 * DFS - Pre-Order
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
 * @param {TreeNode} root
 * @return {number[][]}
 */
var zigzagLevelOrder = (root, level = 0, order = []) => {
    const isBaseCase = (root === null);
    if (isBaseCase) return [];

    return search(root, level, order);
}

var search = (node, level, order) => {
    const isEven = ((level % 2) === 0);
    const action = isEven ? 'push' : 'unshift';
    const newLevel = (order[level] ?? []);

    newLevel[action](node.val);
    order[level] = newLevel;

    return dfsPreOrder(node, level, order);
}

const dfsPreOrder = (node, level, order) => {
    const { left, right } = node;

    zigzagLevelOrder(left, (level + 1), order);  /* Time O(N) | Space O(N) */
    zigzagLevelOrder(right, (level + 1), order);/* Time O(N) | Space O(N) */

    return order;
}

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Please take a look at the updated code.
submission link for the proposed code: https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/submissions/1388722933/

/**
 * BFS
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
 * @param {TreeNode} root
 * @return {number[][]}
 */
var zigzagLevelOrder = (root) => {
    const isEdgeBase = (root === null);
    if (isEdgeBase) return [];
    
    return search(root);/* Time O(N) | Space O(N) */
};

var search = (root, isZigZag = true, order = []) => {
    const queue = new Queue([ root ]);
    
    while (!queue.isEmpty()) {        /* Time O(N) */
        const levels = [];

        bfs(queue, isZigZag, levels); /* Time O(WIDTH) | Space O(WIDTH) */
        order.push(levels);           /*                 Space O(N) */
        isZigZag = !isZigZag;
    }
    
    return order;
}

const bfs = (queue, isZigZag, levels) => {
    for (let level = queue.size(); (0 < level); level--) {/* Time O(WIDTH) */
        const { left, val, right } = queue.dequeue();
    
        if (left) queue.enqueue(left);  /* Space O(WIDTH) */
        if (right) queue.enqueue(right);/* Space O(WIDTH) */
        
        levels.push(val);               /* Space O(N) */
    }

    if (!isZigZag) levels.reverse();
}

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@aakhtar3 (tagging to draw attention to the proposed code)

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@aadil42 Your proposed code looks good. Spacing is also good for this one. Make sure to change your current submission file to reflect your updated code

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@Ykhan799, I updated the code.


const zigzagOrder = [];

while(!q.isEmpty()) {

let size = q.size();
const row = [];

while(size) {
const node = q.dequeue();
row.push(node.val);
if(node.left) q.enqueue(node.left);
if(node.right) q.enqueue(node.right);
size--;
}

if(!isLeft) {
zigzagOrder.push(row.reverse());
}
if(isLeft) {
zigzagOrder.push(row);
}
isLeft = !isLeft;
}

return zigzagOrder;
};