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解題思路

二維字首和。

程式碼

#include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;
const int MAXN = 5005;

inline int rd(){
    int x=0,f=1;char ch=getchar();
    while(!isdigit(ch)) {f=ch=='-'?0:1;ch=getchar();}
    while(isdigit(ch))  {x=(x<<1)+(x<<3
 
)+ch-'0';ch=getchar();}
    return f?x:-x;
}

int n,r,a[MAXN][MAXN],ans;

int main(){
    n=rd(),r=rd();int x,y,w;
    for(int i=1;i<=n;i++){
        x=rd(),y=rd(),w=rd();x++;y++;
        a[x][y]=w;
    }
    for(int i=1;i<=5001;i++)
        for(register int j=1;j<=5001;j++)
            a[i][j]=a[i][j]+a[i-1
 
][j]+a[i][j-1]-a[i-1][j-1];
    for(register int i=r;i<=5001;i++)
        for(register int j=r;j<=5001;j++)
            ans=max(ans,a[i][j]-a[i-r][j]-a[i][j-r]+a[i-r][j-r]);
    cout<<ans<<endl;
    return 0;
}