bzoj1 218 激光炸彈（二位前綴和）

bzoj1 218 激光炸彈

思路：二維前綴和

#include 
using namespace std;
const int N = 5010;
int dp[N][N];
int n, r;
int main(){
#ifdef ONLINE_JUDGE
#else
    freopen("in.txt", "r", stdin);
#endif //ONLINE_JUDGE
    int a, b, c, ans;
    while(~scanf("%d%d", &n, &r)){
        for(int i = 1; i <= n; i++){
            ans = 0;
            scanf("%d%d%d", &a, &b, &c);
            dp[a + 1][b + 1] = c;
        }
        for(int i = 1; i <= 5001; i++){
            for(int j = 1; j <= 5001; j++){
                dp[i][j] += dp[i - 1][j];
            }
        }
        for(int i = 1; i <= 5001; i++){
            for(int j = 1; j <= 5001; j++){
                dp[i][j] += dp[i][j - 1];
            }
        }
        for(int i = r; i <= 5001; i++){
            for(int j = r; j <= 5001; j++){
                ans = max(ans, dp[i][j] - dp[i - r][j] - dp[i][j - r] + dp[i - r][j - r]);
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}