Leetcode-104: Maximum Depth of Binary Tree

这道题比较简单，我就用的递归。应该还可以用queue等方法。
解法1: 递归

#include <iostream>
#include <queue>
#include <vector>
#include <algorithm>


using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

void dfs(TreeNode* node, int depth, int &maxDepth) {
    if (node) {
        if (depth>maxDepth) maxDepth=depth;
        dfs(node->left, depth+1, maxDepth);
        dfs(node->right, depth+1, maxDepth);
    }
}

int maxDepth(TreeNode* root) {
    if (!root) return 0;
    int maxDepth=1;
    dfs(root, 1, maxDepth);
    return maxDepth;
}

int main()
{
    TreeNode t1(3);
    TreeNode t2(9);
    TreeNode t3(20);
    TreeNode t4(15);
    TreeNode t5(7);

    t1.left=&t2;
    t1.right=&t3;
    t3.left=&t4;
    t3.right=&t5;

    cout<<maxDepth(&t1)<<endl;

    return 0;
}