poj3779(二分答案）

#include<cstdio>
#include<algorithm>
using namespace std;

struct my{
    int x,y;
};

my a[1000];
int mid;
int tmp[1000];
int c,n;

bool cmp(const my &a,const my &b){
     return a.x<b.x;
}

bool judge(int l,int r)
{
    int cnt=0;
    for(int i=l; i<=r; ++i) tmp[++cnt]=a[i].y;
    sort(tmp+1,tmp+cnt+1);
    for(int i=c; i<=cnt; ++i)
        if(tmp[i]-tmp[i-c+1]<=mid) return 1;
    return 0;
}
bool check(int x)
{
    int l=1,r=1;
    for(; r<=n; ++r)
    {
        if(a[r].x-a[l].x>x)
            if(judge(l,r-1)) return 1;
        for(; a[r].x-a[l].x>x; ) l++;
    }
    return judge(l,n);
}
int main(){
    int x,y;
    scanf("%d%d",&c,&n);
    for (int i=1;i<=n;i++){
        scanf("%d%d",&x,&y);
        a[i].x=x;
        a[i].y=y;
    }
    sort(a+1,a+1+n,cmp);
    int l=0,r=10000;
    int ans=0;
    while(l<=r){
        mid=(l+r)>>1;
        if(check(mid)){
            r=mid-1;
            ans=mid+1;
        }
        else l=mid+1;
    }
    printf("%d",ans);
return 0;
}