hdu 1081 To The Max 矩阵压缩

#include 
#include 
#include 
#include 

#define inf 0x3f3f3f3f
#define LL long long
using namespace std;

/************************************************

designer:hl
time:2016/11/16
Exe.Time:15 ms
Exe.Memory:1592 KB

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1081

题意：最小子矩阵

题解：矩阵压缩

************************************************/





int main() {
    int n;
    int num[105][105];
    while (~scanf("%d", &n)) {
        int a;
        memset(num, 0, sizeof(num));
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= n; j++) {
                scanf("%d", &a);
                num[i][j] = num[i][j - 1] + a;
            }
        int Max = -inf;
        int ans = -1;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= i; j++) {
                ans = -1;
                for (int k = 1; k <= n; k++) {
                    if (ans > 0)
                        ans += num[k][i] - num[k][j - 1];
                    else
                        ans = num[k][i] - num[k][j - 1];
                    if (ans > Max)
                        Max = ans;
                }
            }
        }
        printf("%d\n", Max);
    }
    return 0;
}