hdu 2665 划分树

思路：裸的划分树

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cmath>
#define Maxn 100010
#define inf 0x7fffffff
#define lson(x) (x<<1)
#define rson(x) ((x<<1)|1)
#define mid ((tree[po].l+tree[po].r)>>1)
using namespace std;
struct Tree{
    int l,r;
}tree[Maxn*4];
int sorted[Maxn];
int val[20][Maxn],toLeft[20][Maxn];
void BuildTree(int l,int r,int dep,int po)
{
    tree[po].l=l,tree[po].r=r;
    if(l==r) return ;
    int same=mid-l+1,i;
    for(i=l;i<=r;i++)
        if(val[dep][i]<sorted[mid])
            same--;
    int lpos=l,rpos=mid+1;
    for(i=l;i<=r;i++)
    {
        if(i==l)
            toLeft[dep][i]=0;
        else
            toLeft[dep][i]=toLeft[dep][i-1];
        if(val[dep][i]<sorted[mid])
            toLeft[dep][i]++,val[dep+1][lpos++]=val[dep][i];
        else
            if(val[dep][i]>sorted[mid])
            val[dep+1][rpos++]=val[dep][i];
        else
            if(same)
            toLeft[dep][i]++,val[dep+1][lpos++]=val[dep][i],same--;
            else
            val[dep+1][rpos++]=val[dep][i];
    }
    BuildTree(l,mid,dep+1,lson(po));
    BuildTree(mid+1,r,dep+1,rson(po));
}
int query(int l,int r,int k,int dep,int po)
{
    if(l==r)
        return val[dep][l];
    int vd,invd;
    if(l==tree[po].l)
        vd=toLeft[dep][r],invd=0;
    else
        vd=toLeft[dep][r]-toLeft[dep][l-1],invd=toLeft[dep][l-1];
    if(vd>=k){
        int newl=tree[po].l+invd;
        int newr=tree[po].l+vd+invd-1;
        return query(newl,newr,k,dep+1,lson(po));
    }
    else{
        int ss=l-tree[po].l-invd;
        int s=r-l+1-vd;
        int newl=mid+ss+1;
        int newr=mid+ss+s;
        return query(newl,newr,k-vd,dep+1,rson(po));
    }
}
int main()
{
    int n,m,i,j,k,s,t,T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        for(i=1;i<=n;i++)
        {
            scanf("%d",&val[0][i]);
            sorted[i]=val[0][i];
        }
        sort(sorted+1,sorted+1+n);
        BuildTree(1,n,0,1);
        for(i=1;i<=m;i++)
        {
            scanf("%d%d%d",&s,&t,&k);
            printf("%d\n",query(s,t,k,0,1));
        }
    }
    return 0;
}