题解 | #JS_从上往下打印二叉树#

二叉树层序遍历
利用队列结构

function PrintFromTopToBottom(root)
{
    // write code here
    if(!root) return []
    let queue = [];
    queue.unshift(root);
    //输出数列
    let res = [];
    while(queue.length > 0){
        let tmp = queue.pop();
        res.push(tmp.val);
        if(tmp.left) queue.unshift(tmp.left);
        if(tmp.right) queue.unshift(tmp.right);
    }
    return res;
}