NC15 求二叉树的层序遍历

https://www.nowcoder.com/practice/04a5560e43e24e9db4595865dc9c63a3

import (
    "container/list"
)

// type TreeNode struct {
//  Val   int
//  Left  *TreeNode
//  Right *TreeNode
// }

/**
 *
 * @param root TreeNode类
 * @return int整型二维数组
 */
func levelOrder(root *TreeNode) [][]int {
    if root == nil {
        return nil
    }
    var result [][]int
    queue := list.New()
    queue.PushBack(root)

    for queue.Len() != 0 {
        size := queue.Len()
        var temp []int
        for i := 0; i < size; i++ {
            ele := queue.Front().Value.(*TreeNode)
            queue.Remove(queue.Front())
            temp = append(temp, ele.Val)
            
            if ele.Left != nil {
                queue.PushBack(ele.Left)
            }

            if ele.Right != nil {
                queue.PushBack(ele.Right)
            }
        }

        result = append(result, temp)
    }

    return result
}