HDU5806：NanoApe Loves Sequence Ⅱ(尺取法）

题目链接：HDU5806

题意：找出有多少个区间中第k大数不小于m.

分析：用尺取法可以搞定，CF以前有一道类似的题目.

 #include<cstdio>
 using namespace std;
 typedef long long ll;
 #define d\n I64d\n
 int T,n,m,K,num,r,a[];
 ll ans;
 int main()
 {
     scanf("%d",&T);
     while (T--)
     {
         scanf("%d%d%d",&n,&m,&K);
         for (int i=;i<=n;i++) scanf("%d",&a[i]);
         num=;r=;ans=;
         for (int i=;i<=n;i++)
         {
             while (num<K&&r<n){r++;num+=(a[r]>=m);}
             if (num<K) break;
             ans+=n-r+;
             num-=(a[i]>=m);
         }
         printf("%d",ans);
     }
 }