POJ 2104 K-th Number （划分树）

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <time.h>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#define met(a,b) memset(a,b,sizeof a)
#define pb push_back
#define lson(x) ((x<<1))
#define rson(x) ((x<<1)+1)
using namespace std;
typedef long long ll;
const int N=1e5+50;
const int M=N*N+10;
struct P_Tree{
    int n,order[N];
    int valu[20][N],num[20][N];
    ll sum[N],lsum[20][N],isum;
    void build(int l,int r,int ind){
        if(l==r)return;
        int mid=(l+r)/2;
        int same=mid-l+1,ln=l,rn=mid+1;
        for(int i=l;i<=r;i++){
            int flag=0;
            if((valu[ind][i]<order[mid])||(valu[ind][i]==order[mid]&&same)){
                flag=1;
                valu[ind+1][ln++]=valu[ind][i];
                lsum[ind][i]=lsum[ind][i-1]+valu[ind][i];
                if(valu[ind][i]==order[mid])same--;
            }
            else {
                valu[ind+1][rn++]=valu[ind][i];
                lsum[ind][i]=lsum[ind][i-1]+valu[ind][i];
            }
            num[ind][i]=num[ind][i-1]+flag;
        }
        build(l,mid,ind+1);
        build(mid+1,r,ind+1);
    }
    void init(int len){
        n=len;sum[0]=0;
        for(int i=0;i<20;i++)valu[i][0]=num[i][0]=lsum[i][0]=0;
        for(int i=1;i<=n;i++){
            scanf("%d",&order[i]);
            valu[0][i]=order[i];
            sum[i]=sum[i-1]+order[i];
        }
        sort(order+1,order+n+1);
        build(1,n,0);
    }
    int query(int s,int t,int k,int l,int r,int ind){
        if(l==r)return valu[ind][l];
        int mid=(l+r)/2;
        int lx=num[ind][s-1]-num[ind][l-1];
        int ly=num[ind][t]-num[ind][s-1];
        int rx=s-1-l+1-lx;
        int ry=t-s+1-ly;
        if(ly>=k)return query(l+lx,l+lx+ly-1,k,l,mid,ind+1);
        else {
            isum+=lsum[ind][t]-lsum[ind][s-1];
            s=mid+1+rx;
            t=mid+1+rx+ry-1;
            return query(s,t,k-ly,mid+1,r,ind+1);
        }
    }
}tree;
int main() {
    int n,m;
    while(~scanf("%d%d",&n,&m)){
        tree.init(n);
        while(m--){
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            printf("%d\n",tree.query(u,v,w,1,n,0));
        }
    }
}