剑指offer-JZ38-二叉树的深度

题目描述

输入一棵二叉树，求该树的深度。从根结点到叶结点依次经过的结点（含根、叶结点）形成树的一条路径，最长路径的长度为树的深度。

C++

1.DFS：计算节点数

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
class Solution {
public:
    int deep = 0;
    vector t;
    int TreeDepth(TreeNode* pRoot)
    {
        Helper(pRoot);
        return deep;
    }
    void Helper(TreeNode* pRoot){
        if(pRoot == NULL){
            int n = t.size();
            deep = max(deep, n);
            return;
        }
        t.push_back(pRoot->val);
        Helper(pRoot->left);
        Helper(pRoot->right);
        t.pop_back();
    }
};

2.递归： 若当前节点为空则返回0，否则返回左右子树深度最大的加1

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
class Solution {
public:
    int TreeDepth(TreeNode* pRoot)
    {
        if(pRoot == 0)
            return 0;
        return max(TreeDepth(pRoot->left),TreeDepth(pRoot->right))+1;
    }
};