111. 二叉树的最小深度

原题

https://leetcode.cn/problems/minimum-depth-of-binary-tree/description/

思路

递归

复杂度

时间：O(n)
空间：O(n)

Python代码

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def minDepth(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0
        if root.left is None and root.right is None:
            return 1
        # 左右子树的最小深度
        leftDepth, rightDepth = float("inf"), float("inf")
        if root.left:
            leftDepth = self.minDepth(root.left)
        if root.right:
            rightDepth = self.minDepth(root.right)
        return min(leftDepth, rightDepth) + 1

Go代码

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func minDepth(root *TreeNode) int {
	if root == nil {
		return 0
	}
	if root.Left == nil && root.Right == nil {
		return 1
	}
	// 子树的最小深度
	leftDepth, rightDepth := math.MaxInt32, math.MaxInt32
	if root.Left != nil {
		leftDepth = minDepth(root.Left)
	}
	if root.Right != nil {
		rightDepth = minDepth(root.Right)
	}
	return 1 + min(leftDepth, rightDepth)
}