K-th Number

区间第K大

题目链接

 #include <stdio.h>
 #include <algorithm>
 #include <vector>
 #include <iostream>
 using namespace std;
 typedef long long ll;
 inline int read()
 {
     int x=,f=;char ch=getchar();
     while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}
     while(ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}
     return x*f;
 }

 /********************************************************************/

 const int maxn = 1e5+;
 int n, m, cnt, root[maxn], a[maxn], x, y, k;

 struct node{
     int l, r, sum;
 }T[maxn*];

 vector<int>v;
 int getid(int x){return lower_bound(v.begin(), v.end(), x) - v.begin() + ;}    //离散化

 void update(int l, int r, int &x, int y, int pos){
     T[++cnt] = T[y], T[cnt].sum++, x = cnt;
     if(l == r) return ;
     int mid = (l+r)>>;
     if(mid >= pos) update(l, mid, T[x].l, T[y].l, pos);
     else update(mid+, r, T[x].r, T[y].r, pos);
 }

 int query(int l, int r, int x, int y, int k){
     if(l == r) return l;
     int mid = (l+r)>>;
     int sum = T[T[y].l].sum - T[T[x].l].sum;
     if(sum >= k) return query(l, mid, T[x].l, T[y].l, k);
     else return query(mid+, r, T[x].r, T[y].r, k-sum);
 }

 int main(){
     n = read(); m = read();
     for(int i = ;i <= n;i++){
         a[i] = read();
         v.push_back(a[i]);
     }
     //离散化
     sort(v.begin(), v.end());
     v.erase(unique(v.begin(), v.end()), v.end());
     //unique 去重
     for(int i = ;i <= n;i++) update(, n, root[i], root[i-], getid(a[i]));
     for(int i = ;i <= m;i++){
         x = read(); y = read(); k = read();
         printf("%d\n", v[query(, n, root[x-], root[y], k) - ]);  //离散化回来
     }
     return ;
 }