自己写的judge函数太丑了，还是错的
//类似滑动窗口

bool judge(int x){
	 int ans=0;int i;int cnt=0;
	for (i=1;i<=n;i++)
	   {
	   if(a[i]>=x) cnt++;
        if (cnt>=k)  break;
	   }
	   ans+=n-i+1;
	   int j=1;
	while (i<=n)
	{
    while (j<=n&&a[j]<x){
        ans+=n-i+1;
        j++;
        }
       while (a[i]<x) i++; 
    }
    return ans<x;
}

正解代码

#include<cstdio>
using namespace std;
typedef long long ll;
int n,k;
ll m;
int a[100005];
bool judge(int x){
	 int ans=0;int i;int cnt=0;
	for (i=1;i<=n;i++)
	   {
	   if(a[i]>=x) cnt++;
        if (cnt>=k)  break;
	   }
	   ans+=n-i+1;
	   int j=1;
	while (i<=n)
	{
    while (j<=n&&a[j]<x){
        ans+=n-i+1;
        j++;
        }
       while (a[i]<x) i++; 
    }
    return ans<x;
}
int main(){
 int T;
 scanf("%d",&T);
 while (T--){
 	scanf("%d%d%lld",&n,&k,&m);
 	for (int i=1;i<=n;i++)
 	  scanf("%d",&a[i]);
 	  int l=1,r=10000000000;
 	  int mid;
 	  while (l<r){
 	  	 mid=(l+r)>>1;
 	  	 if (judge(mid)) l=mid+1;
 	  	 else r=mid;
	   }
	   printf("%d\n",l-1);
   }
  return 0;
}