poj 2104 K-th Number(划分线段树)

//poj 2104 K-th Number(划分线段树)
#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int MAXN=100100;
int st[MAXN];//对所存序列进行排序（取基准元素所用）
struct node
{
int l,r;
}tree[MAXN*4];//建立线段树所用空间
int arrsub[33][MAXN];
int arrl_len[33][MAXN];//计算多少个进入左孩子
int n,m;
void build(int inode,int l,int r,int deep)
{
tree[inode].l=l;tree[inode].r=r;
if(l==r) return ;
int mid=(l+r)/2;
int midv=st[mid];
int ltomid=mid-l+1;
for(int i=l;i<=r;i++)
{
if(arrsub[deep][i]<midv) ltomid--;
}
int lto,rto;
lto=rto=0;
for(int i=l;i<=r;i++)
{
if(i==l)
{
arrl_len[deep][i]=0;
}
else
{
arrl_len[deep][i]=arrl_len[deep][i-1];
}
if(arrsub[deep][i]<midv)
{
arrl_len[deep][i]++;
arrsub[deep+1][l+lto++]=arrsub[deep][i];
}
else if(arrsub[deep][i]>midv)
{
arrsub[deep+1][mid+1+rto++]=arrsub[deep][i];
}
else
{
if(ltomid>0)
{
arrl_len[deep][i]++;
arrsub[deep+1][l+lto++]=arrsub[deep][i];
ltomid--;
}
else
{
arrsub[deep+1][mid+1+rto++]=arrsub[deep][i];
}

}
}
build(inode*2,l,mid,deep+1);
build(inode*2+1,mid+1,r,deep+1);
}
int query(int l,int r,int k,int inode ,int deep)
{
if(l==r) return arrsub[deep][l];
int sum,ts;
if(l==tree[inode].l)
{
ts=0;
}
else
{
ts=arrl_len[deep][l-1];
}
sum=arrl_len[deep][r]-ts;
int ls=tree[inode].l;
int rs=tree[inode].r;
int mid=(ls+rs)/2;
if(sum>=k)
{
return query(ls+ts, ls+arrl_len[deep][r]-1 , k, inode*2 , deep+1);
}
else
{
int ee = l - ls + 1 - ts ;
int e = r - l  - sum ;
return query(mid+ee , mid+ee+e, k-sum , inode*2+1 ,deep+1);
}
}
int main()
{
int a,b,c;
while(scanf("%d%d",&n,&m)==2)
{
for(int i=1;i<=n;i++)
{
scanf("%d",&st[i]);
arrsub[1][i]=st[i];
}
sort(st+1,st+n+1);
build(1,1,n,1);
for(int i=0;i<m;i++){
scanf("%d %d %d",&a,&b,&c);
printf("%d\n",query(a,b,c,1,1));
}
/*for(int i=1;i<=7;i++)
{
printf("%d ",st[i]);
}
printf("\n\n");
for(int i=1;i<=7;i++)
{
for(int j=1;j<=7;j++)
{
printf("%d ",arrsub[i][j]);
}
printf("\n");
}
cout<<endl;
for(int i=1;i<=7;i++)
{
for(int j=1;j<=7;j++)
{
printf("%d",arrl_len[i][j]);
}
printf("\n");
}*/
}
return 0;
}