2016郑州轻工业学院校赛 B 蛤玮的财宝

比赛时没写出来，结束后听ccx学长讲，才知道有多线程DP，感觉自己菜成dog，之前就没听过，还是太弱。

dp：

#include <iostream>
#include <queue>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <stack>
using namespace std;

int dp[222][111][111];
int a[111][111];

#define max4(a,b,c,d) max(max(a,b),max(c,d))

int main()
{
    int t, n, m;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%d%d", &n, &m);
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=m; j++)
            scanf("%d", &a[i][j]);
        }
        memset(dp, 0, sizeof(dp));
        dp[0][1][1] = a[1][1];
        for(int k=1; k<=n+m-2; k++)
        {
            for(int i=1; i<=k+1; i++)
            {
                for(int j=1; j<=k+1; j++)
                {
                    dp[k][i][j] = max4(dp[k-1][i][j], dp[k-1][i-1][j], dp[k-1][i][j-1], dp[k-1][i-1][j-1]);
                    if(i!=j)
                        dp[k][i][j]+=a[i][k+2-i]+a[j][k+2-j];
                    else
                        dp[k][i][j]+=a[i][k+2-i];
                }
            }
        }
        printf("%d
", dp[n+m-2][n][n]);
    }

    return 0;
}

 记忆化搜索

#include <iostream>
#include <queue>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <stack>
using namespace std;

int dp[222][111][111];
int a[111][111];

#define max4(a,b,c,d) max(max(a,b),max(c,d))

int DFS(int k, int i1, int i2)
{
    if(dp[k][i1][i2])
        return dp[k][i1][i2];
    if(k==0||i1==0||i2==0||k+2-i1==0||k+2-i2==0)
        return dp[k][i1][i2];
    dp[k][i1][i2] = max4(DFS(k-1, i1-1, i2), DFS(k-1, i1, i2-1), DFS(k-1, i1-1, i2-1), DFS(k-1, i1, i2));
    if(i1!=i2)
        dp[k][i1][i2] += a[i1][k+2-i1]+a[i2][k+2-i2];
    else
        dp[k][i1][i2] += a[i1][k+2-i1];

    return dp[k][i1][i2];
}

int main()
{
    int t, n, m;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%d%d", &n, &m);
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=m; j++)
            scanf("%d", &a[i][j]);
        }
        memset(dp, 0, sizeof(dp));
        dp[0][1][1] = a[1][1];
        int ans = DFS(n+m-2, n, n);
        printf("%d
", ans);
    }

    return 0;
}