P8612 [蓝桥杯 2014 省 AB] 地宫取宝

https://www.luogu.com.cn/problem/P8612#submit

原始暴搜代码，没有记忆化，会tle

#include<iostream>
#include<vector>
#include<algorithm>
#include<math.h>
#include<sstream>
#include<string>
#include<string.h>
#include<iomanip>
#include<map>
#include<queue>
#include<limits.h>
#include<climits>
using namespace std;
typedef long long ll;

int n, m, k;
int mplst[60][60];
ll ans = 0;
ll mod = 1000000007;
bool vis[60][60] = { 0 };
int del[][2] = { {0,1},{1,0}};
ll dp[60][60];
void dfs(int x,int y,int max,int k_get)//(x,y)，max:当前索取的礼物的最大值，k：当前拿了多少礼物
{
	if(x==n-1 and y==m-1)
	{
		if (k_get == k)
			ans++;
		return;
	}
	if (k_get > k)return;
	if (k_get + n - x + m - y -1< k)return;
	for (int i = 0; i < 2; i++)
	{
		int dx = del[i][0], dy = del[i][1];
		if(x+dx>=0 and x+dx<n and y+dy>=0 and y+dy<m)
		{
				if (!vis[x + dx][y + dy])
				{
					vis[x + dx][y + dy] = 1;
					if (mplst[x + dx][y + dy] > max)
					{
						//get
						dfs(x + dx, y + dy, mplst[x + dx][y + dy], k_get + 1);
						//not get
						dfs(x + dx, y + dy, max, k_get );
					}
					else
						dfs(x + dx, y + dy, max, k_get);
					vis[x + dx][y + dy] = 0;
				}
		}
	}
}
int main()
{
	cin >> n >> m >> k;
	memset(mplst, -1, sizeof(mplst));
	memset(vis, 0, sizeof(vis));
	for (int i = 0; i < n; i++)
		for (int j = 0; j < m; j++)
			cin >> mplst[i][j];
	dfs(0, 0, 0, 0);
	memset(vis, 0, sizeof(vis));
	dfs(0, 0, mplst[0][0], 1);
	ans %= mod;
	cout << ans;
	return 0;
}