luogu 3834 【模板】可持久化线段树 1（主席树）

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<cstdlib>
 5 #include<cstring>
 6 #include<algorithm>
 7 #include<vector>
 8 #include<queue>
 9 #define inf 2139062143
10 #define ll long long
11 #define MAXN 200100
12 using namespace std;
13 inline int read()
14 {
15     int x=0,f=1;char ch=getchar();
16     while(!isdigit(ch)) {if(ch==‘-‘) f=-1;ch=getchar();}
17     while(isdigit(ch)) {x=x*10+ch-‘0‘;ch=getchar();}
18     return x*f;
19 }
20 int n,T,cnt;
21 struct node{int ls,rs,sum;}tr[MAXN<<5];
22 struct data{int val,pos;}g[MAXN];
23 bool cmp(data a,data b) {return a.val<b.val;}
24 int rt[MAXN],rnk[MAXN];
25 void inst(int &k,int x,int l,int r)
26 {
27     //cout<<"I : "<<k<<" "<<x<<" "<<l<<" "<<r<<" "<<cnt<<endl;
28     tr[++cnt]=tr[k];
29     k=cnt,tr[k].sum++;
30     if(l==r) return ;
31     int mid=(l+r)>>1;
32     if(x<=mid) inst(tr[k].ls,x,l,mid);
33     else inst(tr[k].rs,x,mid+1,r);
34 }
35 int query(int k,int a,int b,int l,int r)
36 {
37     //cout<<"Q : "<<k<<" "<<a<<" "<<b<<" "<<l<<" "<<r<<endl;
38     int res=tr[tr[b].ls].sum-tr[tr[a].ls].sum;
39     if(l==r) return l;
40     int mid=(l+r)>>1;
41     if(k<=res) return query(k,tr[a].ls,tr[b].ls,l,mid);
42     else return query(k-res,tr[a].rs,tr[b].rs,mid+1,r);
43 }
44 int main()
45 {
46     n=read(),T=read();int a,b,c;
47     for(int i=1;i<=n;i++) g[i].val=read(),g[i].pos=i;
48     sort(g+1,g+n+1,cmp);
49     for(int i=1;i<=n;i++) rnk[g[i].pos]=i;
50     for(int i=1;i<=n;i++)
51     {
52         rt[i]=rt[i-1];
53         inst(rt[i],rnk[i],1,n);
54     }
55     while(T--)
56     {
57         a=read(),b=read(),c=read();
58         printf("%d\n", g[query(c,rt[a-1],rt[b],1,n)].val);
59     }
60 }