数据结构与算法之树

这是我在牛客网做的leetcode题
题目是
Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
中文大意是：求解二叉树的最小深度
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
/**
求解二叉树的最小深度，用递归的方法解决
*/

public class Solution {
public int run(TreeNode root) {
if(root == null){
return 0;
}
if(root.right == null){
return 1+run(root.left);
}
if(root.left == null){
return 1+run(root.right);
}
if(root.right !=null && root.left != null){
return 1+Math.min(run(root.right),run(root.left));
}
return -1;
}
}

接下来，做个延伸，求解二叉树的最大深度，还是一递归的方式求解（有时间可以试试深度优先搜索DFS思维）

public int runMax(TreeNode root){
return root== null ?0:Math.max(runMax(root.left), runMax(root.right));
}