Day1-T1

原题目

　　Describe：普通前缀和（当然有升级版的题目，范围3000+）

　　code：　　

#include<bits/stdc++.h>
#define maxn 1010
#define INF 1010010101
#define eps 1e-9
#define rep1(x,y) for(register int i=x;i<=y;i++)
#define rep2(x,y) for(register int j=x;j<=y;j++)
#define rep3(x,y) for(register int k=x;k<=y;k++)
#define rep4(x,y) for(register int l=x;l<=y;l++)
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
typedef double db;
bool f[55][55];
LL r,c,n,K,s[55][55];
LL ans,now;
int x,y;
inline int read(){
    int ret=0,f=1;char ch=getchar();
    while (ch<'0'||ch>'9') {if (ch=='-') f=-f;ch=getchar();}
    while (ch>='0'&&ch<='9') ret=ret*10+ch-'0',ch=getchar();
    return ret*f;
}
inline void write(LL x){
    if(x<0){putchar('-'),write(-x);return;}
    if(x/10)write(x/10);putchar(x%10+'0');
}
inline double Read(){
    double X=0,Y=1.0;int w=0;char ch=0;
    while(!isdigit(ch)){w|=ch=='-';ch=getchar();}
    while(isdigit(ch))X=X*10+(ch^48),ch=getchar();
    ch=getchar();
    while(isdigit(ch)) X+=(Y/=10)*(ch^48),ch=getchar();
    return w?-X:X;
}
int main(){
    freopen("Orchestra.in","r",stdin);                              
    freopen("Orchestra.out","w",stdout);
    r=read();c=read();n=read();K=read();
    rep1(1,n)x=read(),y=read(),f[x][y]=1;
    rep1(1,r)rep2(1,c){s[i][j]=s[i-1][j]+f[i][j]+s[i][j-1]-s[i-1][j-1];}
    for(int i=1;i<=r;i++){
        for(int j=1;j<=c;j++){
            for(int k=i;k<=r;k++){
                for(int l=j;l<=c;l++){        
                    now=s[k][l]-s[i-1][l]-s[k][j-1]+s[i-1][j-1];
                    if(now>=K)ans++;
                }
            }
        }
    }
    write(ans);
    return 0;
}