poj1050

经典的最大子矩阵和。。

转化成最大子段和

（通过枚举列的长度，然后对于选定的那一列做一次的最长子段和）最后选取最大就是答案。。

 1 /*
 2  State:Accepted
 3  Time:2013.3.1
 4 */
 5 
 6 #include <iostream>
 7 #include <cstdlib>
 8 #include <cstdio>
 9 #include <cstring>
10 #include <algorithm>
11 #include <fstream>
12 #include <string>
13 #include <cmath>
14 using namespace std;
15 int n , a[150][150] ,f[200], sumrow[200][200] , ans ;
16 
17 void init(){      
18       scanf("%d",&n);
19       for (int i = 1; i <= n; ++i)
20           for (int j = 1; j <= n; ++j){
21               scanf("%d",&a[i][j]);
22               sumrow[i][j] = sumrow[i - 1][j] + a[i][j];
23           }
24       
25 }
26 
27 void dp(){
28      int nowv;
29      ans = -1000000;
30      for (int l = 1; l <= n; ++l)
31         for (int r = l; r <= n; ++r){
32             for (int i = 1; i <= n; ++i)  f[i] = -1000000;
33             for (int i = 1; i <= n; ++i){
34                nowv = sumrow[r][i] - sumrow[l - 1][i];
35                f[i] = max(nowv , f[i -1] + nowv);
36                ans  = max(ans , f[i]);
37             }
38         }
39      printf("%d\n",ans);
40      
41 }
42 int main(){
43       freopen("poj1050.in","r",stdin);
44       freopen("poj1050.out","w",stdout);
45       init();
46       dp();
47       fclose(stdin);
48       fclose(stdout);
49 }

 

posted on 2013-03-23 19:58  yzcstc  阅读(243)  评论(0)  编辑  收藏  举报