贪心之最大子矩阵和

O(N^3)

#include<stdio.h>#include<stdlib.h>const int maxn=101;int a[maxn][maxn],s[maxn][maxn];int main(){int i,j,k,m,n,u,v;int x,y;scanf("%d",&n);for(i=1;i<=n*n;i++){scanf("%d",&k);x=(i-1)/n+1;y=i%n;if(y==0)y=n;a[x][y]=k;}for(i=1;i<=n;i++)for(j=1;j<=n;j++)s[i][j]=s[i-1][j]+a[i][j];int max=s[1][1];for(i=1;i<=n;i++)for(j=i;j<=n;j++){m=0;for(k=1;k<=n;k++){if(m>0)m+=s[j][k]-s[i-1][k];else m=s[j][k]-s[i-1][k];if(m>max)max=m;}}printf("%d\n",max);return 0;}