2022-10-10

[Zheaoli]

2022-10-10

[gongpeione]

/*
 * @lc app=leetcode id=102 lang=typescript
 *
 * [102] Binary Tree Level Order Traversal
 */

// @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)
 *     }
 * }
 */
/**
 * 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 levelOrder(root: TreeNode | null): number[][] {
    const ans = [] as number[][];
    const queue = [] as TreeNode[];

    queue.push(root);

    while (queue.length) {
        const levelVal = [] as number[];
        const len = queue.length;

        for (let i = 0; i < len; i++) {
            const node = queue.shift();

            if (node) {
                levelVal.push(node.val);
                node.left && queue.push(node.left);
                node.right && queue.push(node.right);
            }
        }

        // make sure level is not empty
        levelVal.length && ans.push(levelVal);
    }

    return ans;
};
// @lc code=end

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