力扣（LeetCode）104. 二叉树的最大深度

思路：
递归一下，如果理解有困难，建议自己动手画一下二叉树，三四个结点即可，方便理解

注释掉的代码产生的结果可能是正确的，但是超时了

#include<iostream>
#include<cstdlib>
using namespace std;

typedef struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
} TreeNode,*SearchTree,*Position;

void PreOrderTraversal(SearchTree T)
{
    if(T==NULL)
        return;
    cout<<T->val<<" ";
    PreOrderTraversal(T->left);
    PreOrderTraversal(T->right);
}

SearchTree Insert(int val,SearchTree T)
{
    if(T==NULL)
    {
        T = (SearchTree)malloc(sizeof(TreeNode));
        if(T==NULL)
        {
            cout<<"MALLOC ERROR\n"<<endl;
            exit(1);
        }
        T->val = val;
        T->left = T->right = NULL;
    }
    else
    {
        if(val>T->val)
            T->right = Insert(val,T->right);
        else if(val<T->val)
            T->left = Insert(val,T->left);
    }
    return T;
}

class Solution
{
public:


    int maxDepth(TreeNode* root)
    {
        if(root == NULL)
            return 0;
        int Ldepth=1,Rdepth=1;

        if(root->left)
            Ldepth = maxDepth(root->left)+1;

        if(root->right)
            Rdepth = maxDepth(root->right)+1;

        return Ldepth>Rdepth ? Ldepth : Rdepth;
    }
};


//class Solution
//{
//public:
//    int maxDepth(TreeNode* root)
//    {
//        if(root == NULL)
//            return 0;
//
//        return maxDepth(root->left) > maxDepth(root->right) ?
//               maxDepth(root->left)+1 : maxDepth(root->right)+1;
//    }
//};

int main()
{

    Solution s;
    SearchTree T1 = NULL;
    SearchTree T2 = NULL;

    T1 = Insert(3,T1);
    T1 = Insert(9,T1);
    T1 = Insert(20,T1);
    T1 = Insert(15,T1);
    T1 = Insert(7,T1);
//    T1 = Insert(6,T1);
//    T1 = Insert(9,T1);



    PreOrderTraversal(T1);
    cout<<endl;

    int depth;
    depth = s.maxDepth(T1);
    cout<<depth<<endl;

    return 0;
}