本文主要是介绍POJ 2761 Feed the dogs（划分树），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
裸的划分树，直接上代码了。
如果不懂划分树：http://blog.csdn.net/shiqi_614/article/details/8041390
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define MID(a,b) (a+((b-a)>>1))
typedef long long LL;
const int N=1e5+5;
struct P_Tree
{int n,order[N];int valu[20][N],num[20][N];LL sum[N],lsum[20][N],isum;void init(int len){n=len; sum[0]=0;for(int i=0;i<20;i++) valu[i][0]=0,num[i][0]=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+1+n);build(1,n,0);}void build(int lft,int rht,int ind){if(lft==rht) return;int mid=MID(lft,rht);int same=mid-lft+1,ln=lft,rn=mid+1;for(int i=lft;i<=rht;i++)if(valu[ind][i]<order[mid]) same--;for(int i=lft;i<=rht;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];}num[ind][i]=num[ind][i-1]+flag;}build(lft,mid,ind+1);build(mid+1,rht,ind+1);}int query(int st,int ed,int k,int lft,int rht,int ind){if(lft==rht) return valu[ind][lft];int mid=MID(lft,rht);int lx=num[ind][st-1]-num[ind][lft-1];int ly=num[ind][ed]-num[ind][st-1];int rx=st-1-lft+1-lx;int ry=ed-st+1-ly;if(ly>=k) return query(lft+lx,lft+lx+ly-1,k,lft,mid,ind+1);else {isum+=lsum[ind][ed]-lsum[ind][st-1];st=mid+1+rx;ed=mid+1+rx+ry-1;return query(st,ed,k-ly,mid+1,rht,ind+1);}}
}tree;
int main()
{int n,m;while(scanf("%d%d",&n,&m)!=EOF){tree.init(n);for(int i=0;i<m;i++){int a,b,c;scanf("%d%d%d",&a,&b,&c);int res=tree.query(a,b,c,1,n,0);printf("%d\n",res);}}return 0;
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