POJ2104 K-th Number 不带修改的主席树 线段树

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cmath>
 6 #define LL long long
 7 const LL maxn=100010;
 8 using namespace std;
 9 int n,m;
10 struct node{
11     int lc,rc,sum;
12 }t[maxn*20];int tot;
13 struct nod{
14     int x,id;
15 }a[maxn];
16 int rk[maxn]={},rt[maxn]={};
17 bool mcmp(nod aa,nod bb){return aa.x<bb.x;}
18 void insert(int &x,int l,int r,int num){
19     t[++tot]=t[x]; ++t[tot].sum;x=tot;//cout<<t[x].sum<<endl;
20     if(l==r)return;
21     int mid=(r+l)/2;
22     if(num<=mid)insert(t[x].lc,l,mid,num);
23     else insert(t[x].rc,mid+1,r,num);
24 }
25 int getit(int x,int y,int k,int l,int r){
26     if(l==r)return l;
27     int z=t[t[y].lc].sum-t[t[x].lc].sum;
28     int mid=(r+l)/2;
29     if(k<=z)return getit(t[x].lc,t[y].lc,k,l,mid);
30     else return getit(t[x].rc,t[y].rc,k-z,mid+1,r);
31 }
32 int main(){
33     while(~scanf("%d%d",&n,&m)){
34         tot=0;
35         for(int i=1;i<=n;i++){scanf("%d",&a[i].x);a[i].id=i;}
36         sort(a+1,a+1+n,mcmp);
37         for(int i=1;i<=n;i++) rk[a[i].id]=i; 
38         for(int i=1;i<=n;i++){rt[i]=rt[i-1]; insert(rt[i],1,n,rk[i]);}
39         int x,y,k;
40         for(int i=1;i<=m;i++){
41             scanf("%d%d%d",&x,&y,&k);
42             printf("%d\n",a[getit(rt[x-1],rt[y],k,1,n)].x);
43         }
44     }
45     return 0;
46 }