111. 二叉树的最小深度

递归解决

package main
import (
    "fmt"
)
type TreeNode struct {
    Val   int
    Left  *TreeNode
    Right *TreeNode
}
var min = 1<<63 - 1
func minDepth(root *TreeNode) int {
    if root == nil {
        return 0
    }
    dfs(root, 1) //深度递归
    return min
}
func dfs(node *TreeNode, depth int) {
    if node.Right == nil && node.Left == nil { //递归结束条件
        if depth < min {
            min = depth
        }
        return
    }
    if node.Left != nil { // 遍历左节点
        dfs(node.Left, depth+1)
    }
    if node.Right != nil { // 遍历右节点
        dfs(node.Right, depth+1)
    }
}
func main() {
    a := &TreeNode{
        Val: 3,
    }
    b := &TreeNode{
        Val: 9,
    }
    a.Left = b
    c := &TreeNode{
        Val: 20,
    }
    a.Right = c
    d := &TreeNode{
        Val: 15,
    }
    c.Left = d
    e := &TreeNode{
        Val: 7,
    }
    c.Right = e
    fmt.Println(minDepth(a))
}