划分树模板

来源：互联网发布：丰县淘宝编辑：程序博客网时间：2024/09/21 09:19
POJ2104
//划分树，查询区间第k大
原理以后补上。
#include <set>#include <map>#include <list>#include <cmath>#include <ctime>#include <deque>#include <queue>#include <stack>#include <cctype>#include <cstdio>#include <string>#include <vector>#include <cassert>#include <cstdlib>#include <cstring>#include <sstream>#include <iostream>#include <algorithm>using namespace std;//划分树，查询区间第k大const int MAXN = 100010;int tree[20][MAXN]; // 表示每层每个位置的值int sorted[MAXN]; // 已经排好序的数int toleft[20][MAXN] ;// toleft[p][i] 表示第i层从1到i有数分入左边void build(int l,int r,int dep){    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] < sorted[mid])            same--;    int lpos = l;    int rpos = mid + 1;    for(int i=l;i<=r;i++){        if(tree[dep][i] < sorted[mid])            tree[dep+1][lpos++] = tree[dep][i];        else if(tree[dep][i] == sorted[mid] && same > 0){            tree[dep + 1][lpos++] = tree[dep][i];            same--;        }        else            tree[dep+1][rpos++] = tree[dep][i];        toleft[dep][i] = toleft[dep][l-1] + lpos - l;    }    build(l,mid,dep+1);    build(mid+1,r,dep+1);}//查询区间第K大的数，[L,R]是大区间，[l,r]是要查询的小区间int query(int L,int R,int l,int r,int dep,int k){    if(l == r) return tree[dep][l];    int mid = (L+R) >> 1;    int cnt = toleft[dep][r] - toleft[dep][l-1];    if(cnt >= k){        int newl = L + toleft[dep][l-1] - toleft[dep][L-1];        int newr = newl + cnt - 1;        return query(L,mid,newl,newr,dep+1,k);    }    else{        int newr = r + toleft[dep][R] - toleft[dep][r];        int newl = newr - (r - l - cnt);        return query(mid+1,R,newl,newr,dep+1,k - cnt);    }}int main(){    int n,m;    while(scanf("%d%d",&n,&m) == 2){        memset(tree,0,sizeof tree);        for(int i=1;i<=n;i++){            scanf("%d",&tree[0][i]);            sorted[i] = tree[0][i];        }        sort(sorted+1,sorted+n+1);        build(1,n,0);        int s,t,k;        while(m--){            scanf("%d%d%d",&s,&t,&k);            printf("%d\n",query(1,n,s,t,0,k));        }    }    return 0;}
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