题解 | #求二叉树的层序遍历#

/*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)
 *     }
 * }
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param root TreeNode类 
 * @return int整型二维数组
 */
export function levelOrder(root: TreeNode): number[][] {
    // write code here
    const result = []
    const queue = [] //队列存储
    //放置根节点
    queue.push(root)
    while(queue.length){
        const preSize = queue.length
        const floor = [] //记录每一行的元素
        if(root == null){
            return[]
        }
        for(let i = 0;i < preSize;i++){
            const  m = queue.shift()
            floor.push(m.val)
            if(m.left !== null){
                queue.push(m.left)
            }
            if(m.right !== null){
                queue.push(m.right)
            }
        }
        result.push(floor)
    }
    return result
}