package main

import "math"

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

func minDepth(root *TreeNode) (res int) {
	if root == nil {
		return 0
	}
	var dfs func(node *TreeNode, floor int)
	res = math.MaxInt32
	dfs = func(node *TreeNode, floor int) {
		if node == nil {
			return
		}
		if node.Left == nil && node.Right == nil && floor < res {
			res = floor
		}
		dfs(node.Left, floor+1)
		dfs(node.Right, floor+1)

	}
	dfs(root, 1)
	return
}