2016秋季练习

来源：POJ2104

划分树：

#include<iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;int n,Qm;const int MAXN = 100010;int a[MAXN];int tree[20][MAXN];int tol[20][MAXN];void build(int dep,int l,int r){    if(l == r) return ;    int mid = (l+r)>>1;    int same = mid-l+1;    for(int i=l;i<=r;i++) {        if(tree[dep][i] < a[mid]) same -- ;    }    int lpos = l;    int rpos = mid+1;    for(int i=l;i<=r;i++) {        if(tree[dep][i] < a[mid])            tree[dep+1][lpos++] = tree[dep][i];        else if(tree[dep][i] == a[mid] && same > 0){            tree[dep+1][lpos++] = tree[dep][i];            same -- ;        }        else            tree[dep+1][rpos++] = tree[dep][i];        tol[dep][i] = tol[dep][l-1]+lpos-l;    }    build(dep+1,l,mid);    build(dep+1,mid+1,r);}int query(int left,int right,int l,int r,int dep,int k){//    cout<<left<<" "<<right<<" "<<l<<" "<<r<<" "<<dep<<endl;    if(l == r) return tree[dep][l];    int mid = (left+right)>>1;    int cnt = tol[dep][r]-tol[dep][l-1];    if(cnt>=k){        int newl = left+tol[dep][l-1]-tol[dep][left-1];        int newr = newl+cnt-1;        return query(left,mid,newl,newr,dep+1,k);    }    else{        int newr = r+tol[dep][right]-tol[dep][r];        int newl = newr-(r-l-cnt);        return query(mid+1,right,newl,newr,dep+1,k-cnt);    }}int main(){    int l,r,k;    while(scanf("%d%d",&n,&Qm)==2){        memset(tree,0,sizeof tree);        for(int i=1;i<=n;i++) {            scanf("%d",a+i);            tree[0][i] = a[i];        }        sort(a+1,a+1+n);        build(0,1,n);        while(Qm--){            scanf("%d%d%d",&l,&r,&k);            printf("%d\n",query(1,n,l,r,0,k));        }    }    return 0;}