【DP】 cf 321E

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用四边形优化一下dp即可。。。。

#include <bits/stdc++.h>using namespace std;typedef long long LL;const int maxm = 808;const int maxn = 4004;const int INF = 0x3f3f3f3f;int f[maxm][maxn];int s[maxm][maxn];int a[maxn][maxn];int n, m;void read(int &x){x = 0;char ch = getchar();while(ch == ' ' || ch == '\n') ch = getchar();while(ch != ' ' && ch != '\n') x = x * 10 + ch - '0', ch = getchar();}int calc(int i, int j){return a[j][j] - a[i-1][j] - a[j][i-1] + a[i-1][i-1];}void work(){scanf("%d%d", &n, &m);for(int i = 1; i <= n; i++)for(int j = 1; j <= n; j++) read(a[i][j]);for(int i = 1; i <= n; i++)for(int j = 1; j <= n; j++)a[i][j] += a[i][j-1];for(int i = 1; i <= n; i++)for(int j = 1; j <= n; j++)a[i][j] += a[i-1][j];memset(f, INF, sizeof f);f[0][0] = 0;for(int i = 1; i <= m; i++)for(int j = n; j >= 1; j--) {for(int k = s[i-1][j]; k <= (j == n ? n : s[i][j+1]) && k < j; k++) {if(f[i][j] > f[i-1][k] + calc(k+1, j)) {f[i][j] = f[i-1][k] + calc(k+1, j);s[i][j] = k;}}}printf("%d\n", f[m][n] / 2);}int main(){//freopen("data", "r", stdin);work();return 0;}

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