hdu_5806_NanoApe Loves Sequence Ⅱ(双指针)

题目链接：hdu_5806_NanoApe Loves Sequence Ⅱ

题意：

给你一段数，问你有多少个区间满足第K大的数不小于m

题解：

直接双指针加一下区间就行

 #include<cstdio>
 #include<algorithm>
 #define F(i,a,b) for(int i=a;i<=b;i++)
 using namespace std;
 typedef long long ll;
 const int N=2e5+;
 int t,n,k,m;
 int a[N];
 int main()
 {
     scanf("%d",&t);
     while(t--)
     {
         scanf("%d%d%d",&n,&m,&k);
         F(i,,n)scanf("%d",a+i);
         int l=,r=,all=;
         ll ans=;
         while(r<n)
         {
             while(r<n&&all<k)
             {
                 r++;
                 if(a[r]>=m)all++;
             }
             if(r==n&&all<k)break;
             if(all==k)ans+=n-r+;
             while(all==k)
             {
                 if(a[l]>=m)all--;
                 l++;
                 if(all==k)ans+=n-r+;
             }
         }
         printf("%I64d\n",ans);
     }
     return ;
 }