uva 108(最大连续矩阵和)

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题意：给一个n×n的矩阵，求这个矩阵的子矩阵和最大的值。

题解：暴力枚举O(n^6)超时后，看网上是将矩阵中矩阵左上角到各个位置的和都先求出来保存，避免重复计算，果断用了。

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;const int N = 105;const int INF = -0x3f3f3f3f;int main() {int n, s[N][N], sum[N][N], x, y, maxx;while (scanf("%d", &n) != EOF) { maxx = INF;for (int i = 1; i <= n; i++)for (int j = 1; j <= n; j++)scanf("%d", &s[i][j]);for (int i = 0; i < n; i++)sum[i][0] = sum[0][i] = 0;for (int i = 1; i <= n; i++)for (int j = 1; j <= n; j++)sum[i][j] = sum[i][j - 1] + sum[i - 1][j] - sum[i - 1][j - 1] + s[i][j];//减掉重复的for (int i = 1; i <= n; i++)for (int j = i; j <= n; j++)for (int p = 1; p <= n; p++)for (int q = p; q <= n; q++) {int temp = sum[j][q] - sum[j][p - 1] - sum[i - 1][q] + sum[i - 1][p - 1];//加上多减的if (temp > maxx)maxx = temp;}printf("%d\n", maxx);}return 0;}

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