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=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

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

const int maxn = 1e5+7;
int n, m, cnt, root[maxn], a[maxn], x, y, k;

struct node{
    int l, r, sum;
}T[maxn*40];

vector<int>v;
int getid(int x){return lower_bound(v.begin(), v.end(), x) - v.begin() + 1;}    //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)>>1;
    if(mid >= pos) update(l, mid, T[x].l, T[y].l, pos);
    else update(mid+1, 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)>>1;
    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+1, r, T[x].r, T[y].r, k-sum);
}

int main(){
    n = read(); m = read();
    for(int i = 1;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 = 1;i <= n;i++) update(1, n, root[i], root[i-1], getid(a[i]));
    for(int i = 1;i <= m;i++){
        x = read(); y = read(); k = read();
        printf("%d
", v[query(1, n, root[x-1], root[y], k) - 1]);  //离散化回来
    }
    return 0;
}