package main
import . "nc_tools"
/*
 * type TreeNode struct {
 *   Val int
 *   Left *TreeNode
 *   Right *TreeNode
 * }
 */

func TreeDepth(root *TreeNode ) int {
    if root == nil {
        return 0
    }
    queue := []*TreeNode{}
    queue = append(queue, root)
    var depth int
    for len(queue) > 0 {
        size := len(queue)
        for size > 0 {
            //custom queue
            cur := queue[0]
            queue = queue[1:]
            if cur.Left != nil {
                queue = append(queue, cur.Left)
            }
            if cur.Right != nil {
                queue = append(queue, cur.Right)
            }
            size--
        }
        depth++
    }
    return depth
}