主席树

#include<cstdio>
#include<cstring>
#include<algorithm>
#define mid (l+r)/2
using namespace std;

const int N = 200010;
int n, q, m, cnt = 0;
int a[N], b[N], T[N];
int sum[N<<5], L[N<<5], R[N<<5];

inline int build(int l, int r)
{
    int rt = ++ cnt;
    sum[rt] = 0;
    if (l < r){
        L[rt] = build(l, mid);
        R[rt] = build(mid+1, r);
    }
    return rt;
}

inline int update(int pre, int l, int r, int x)
{
    int rt = ++ cnt;
    L[rt] = L[pre]; R[rt] = R[pre]; sum[rt] = sum[pre]+1;
    if (l < r){
        if (x <= mid) L[rt] = update(L[pre], l, mid, x);
        else R[rt] = update(R[pre], mid+1, r, x);
    }
    return rt;
}

inline int query(int u, int v, int l, int r, int k)
{
    if (l >= r) return l;
    int x = sum[L[v]] - sum[L[u]];
    if (x >= k) return query(L[u], L[v], l, mid, k);
    else return query(R[u], R[v], mid+1, r, k-x);
}

int main()
{
    scanf("%d%d", &n, &q);
    for (int i = 1; i <= n; i ++){
        scanf("%d", &a[i]);
        b[i] = a[i];
    }
    sort(b+1, b+1+n);
    m = unique(b+1, b+1+n)-b-1;
    T[0] = build(1, m);
    for (int i = 1; i <= n; i ++){
        int t = lower_bound(b+1, b+1+m, a[i])-b;
        T[i] = update(T[i-1], 1, m, t);
    }
    while (q --){
        int x, y, z;
        scanf("%d%d%d", &x, &y, &z);
        int t = query(T[x-1], T[y], 1, m, z);
        printf("%d\n", b[t]);
    }
    return 0;
}

 

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
const int N = 100000 + 5;

vector<int>node[N << 2];

int T, n, q, ql, qr, ans, k, sz;

int a[N], b[N];

inline int read(){//快速读入是邪教
    char c;
    int ret = 0;
    int sgn = 1;
    do{c = getchar();}while((c < '0' || c > '9') && c != '-');
    if(c == '-') sgn = -1; else ret = c - '0';
    while((c = getchar()) >= '0' && c <= '9') ret = ret * 10 + (c - '0');
    return sgn * ret;
}

void Build(int o, int l, int r){
    node[o].clear();
    if(l == r){
        node[o].push_back(a[l]);
        return ;
    }
    int m = (l + r) >> 1;
    Build(o << 1, l, m);
    Build(o << 1|1, m + 1, r);
    node[o].resize(r - l + 1);
    merge(node[o<<1].begin(), node[o<<1].end(), node[o<<1|1].begin(), node[o<<1|1].end(), node[o].begin());
}

int query(int o, int l, int r, int x){
    //if(ql > r || qr < l) return 0;
    if(ql <= l && qr >= r)  return upper_bound(node[o].begin(), node[o].end(), x) - node[o].begin();
    int m = (l + r) >> 1;
    int ret = 0;
    if(ql <= m)ret += query(o << 1, l, m, x);
    if(qr > m)ret += query(o << 1|1, m + 1, r, x);
    return ret;
}

void work(){
    //ql = read();
    //qr = read();
    //k = read();
    scanf("%d%d%d", &ql, &qr, &k);
    int lt = 1, rt = sz;
   while(lt <= rt){
       int md = (lt + rt) >> 1;
       if(query(1, 1, n, b[md]) >= k)rt = md - 1;
       else lt = md + 1;
   }
   printf("%d\n", b[rt+1]);
}

int main(){
    scanf("%d", &T);
    while(T--){
        scanf("%d%d", &n, &q);
        //n = read();
        //q = read();
        //for(int i = 1; i <= n; i ++) a[i] = b[i] = read();
        for(int i = 1; i <= n; i ++)scanf("%d", a + i), b[i] = a[i];
        Build(1, 1, n);
        sort(b + 1, b + n + 1);
        sz = unique(b + 1, b + n + 1) - (b + 1);
        while(q --)work();
    }
    return 0;
}