bzoj 5085: 最大——结论题qwq

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using std::swap;
using std::min;
using std::max;
const int M=2e3+7;
char buf[M*M*11],*ptr=buf-1;
int read(){
    int ans=0,f=1,c=*++ptr;
    while(c<‘0‘||c>‘9‘){if(c==‘-‘) f=-1; c=*++ptr;}
    while(c>=‘0‘&&c<=‘9‘){ans=ans*10+(c-‘0‘); c=*++ptr;}
    return ans*f;
}
int n,m,k,s[M][M],cnt,sum,ans;
struct pos{
    int x,y,w;
    bool operator <(const pos& h)const{return w>h.w;}
}q[M*M];
int main(){
    fread(buf,1,sizeof(buf),stdin);
    n=read(); m=read(); k=std::min(4*n,n*m);
    for(int i=0;i<n;i++) for(int j=0;j<m;j++) 
    s[i][j]=read(),q[cnt++]=(pos){i,j,s[i][j]};
    std::nth_element(q,q+k,q+cnt);
    for(int i=0;i<k;i++){
        for(int j=0;j<i;j++)if(q[i].x!=q[j].x&&q[i].y!=q[j].y){
            sum=min(s[q[i].x][q[i].y],s[q[j].x][q[j].y]);
            sum=min(sum,s[q[i].x][q[j].y]);
            sum=min(sum,s[q[j].x][q[i].y]);
            ans=max(ans,sum);
        }
    }printf("%d\n",ans);
    return 0;
}