HDU-6231(二分+双指针)

#include <cstdio>
#include <algorithm>
using namespace std;
int n,k;
long long m;
int a[100005];
int b[100005];
long long judge(int x)
{
    int ll=1,num=0;
    long long ans=0;
    for(int i = 1;i <= n;++i)
    {
        if(a[i]>=x)
            num++;
        if(num==k)
        {
            ans+=n-i+1;
            while(a[ll]<x)//双指针移动
            {
                ans+=n-i+1;
                ll++;
            }
            num--;
            ll++;
        }
    }
    return ans;
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d%lld",&n,&k,&m);//m会超过int
        for(int i = 1;i <= n;++i){
            scanf("%d",&a[i]);
            b[i]=a[i];
        }
        sort(b+1,b+1+n);
        int num=unique(b+1,b+1+n)-b-1;
        int l=1,r=num;
        while(l<=r)
        {
            int mid=l+r>>1;
            long long temp=judge(b[mid]);
            if(temp<m)
                r=mid-1;
            else if(temp>=m)
                l=mid+1;
        }
        printf("%d\n",b[r]);
    }
    return 0;
}