HDU 2686 Matrix 多线程dp

Posted 2020-10-15 lemonsbiscuit

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2686

思路:多线程dp，参考51Nod 1084:http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1084

注：这道题用滚动数组优化反而WA，压到三维即可

代码：

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int ans[30][30],dp[60][30][30];
 4 int main() {
 5     int n;
 6     while(~scanf("%d",&n)) {
 7         for(int i=1;i<=n;++i)
 8             for(int j=1;j<=n;++j) 
 9                 scanf("%d",&ans[i][j]);
10         memset(dp,0,sizeof(dp));
11         dp[0][1][1]=ans[1][1];//一步都没走
12         for(int tot=1;tot<=n+n-2;++tot)//走了几步
13             for(int i=1;i<=n&&(i-1<=tot);++i)
14                 for(int j=1;j<=n&&(j-1<=tot);++j) {
15                     dp[tot][i][j]=max(dp[tot][i][j],dp[tot-1][i-1][j-1]);
16                     dp[tot][i][j]=max(dp[tot][i][j],dp[tot-1][i-1][j]);
17                     dp[tot][i][j]=max(dp[tot][i][j],dp[tot-1][i][j-1]);
18                     dp[tot][i][j]=max(dp[tot][i][j],dp[tot-1][i][j])+ans[i][tot+2-i]+ans[j][tot+2-j];
19                     if(i==j) dp[tot][i][j]-=ans[i][tot+2-i];
20                 }
21         printf("%d\n",dp[n+n-2][n][n]);
22     }
23     return 0;
24 }

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