【HDU】2665Kth number（划分树）

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只是为了存模板~

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn = 100005;
int n,m;
int sorted[maxn];
int tree[20][maxn];     //第i层归并之后的结果
int toleft[20][maxn];   //第i层第j个数左边有几个分到左边(包括j自己)
void build(int l,int r,int d){
    if(l == r) return;
    int mid = (l + r) >> 1;
    int same = mid - l + 1;
    for(int i = l;i <= r; i++)
        if(tree[d][i] < sorted[mid])
            same --;
    int lpos = l,rpos = mid + 1;
    toleft[d][0] = 0;
    for(int i = l; i <= r; i++){
        toleft[d][i] = toleft[d][i - 1];
        if(tree[d][i] < sorted[mid]){
            tree[d + 1][lpos++] = tree[d][i];
            toleft[d][i] ++;
        }
        else{
            if(tree[d][i] == sorted[mid] && same > 0){
                same --;
                tree[d + 1][lpos++] = tree[d][i];
                toleft[d][i] ++;
            }
            else
                tree[d + 1][rpos++] = tree[d][i];
        }
    }
    build(l,mid,d + 1);
    build(mid + 1,r,d + 1);
}
int query(int L,int R,int l,int r,int d,int k){
    //printf("%d %d %d %d %d\n",L,R,l,r,d);
    if(l == r) return tree[d][l];
    int mid = (L + R) >> 1;
    int cnt = toleft[d][r] - toleft[d][l - 1];                  //比mid小，但是不在[L,l - 1]内的数的个数
    if(cnt >= k){
        int newl = L + toleft[d][l - 1] - toleft[d][L - 1];
        int newr = newl + cnt - 1;
        return query(L,mid,newl,newr,d + 1,k);
    }
    else{
        int newr = r + toleft[d][R] - toleft[d][r];
        int newl = newr - (r - l - cnt);
        return query(mid + 1,R,newl,newr,d + 1,k - cnt);
    }
}
void debug(int v){
    for(int i = 1; i <= n; i++)
        printf("%d ",sorted[i]);
    puts("");
    for(int i = 1; i <= n; i++){
        printf("%d ",toleft[v][i]);
    }
    puts("");
}
int main(){
    int T;
    scanf("%d",&T);
    while(T--){
        scanf("%d%d",&n,&m);
        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);
        //debug(0);
        for(int i = 0; i < m; i++){
            int x,y,k;
            scanf("%d%d%d",&x,&y,&k);
            printf("%d\n",query(1,n,x,y,0,k));
        }
    }
    return 0;
}

【HDU】2665Kth number（划分树）

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原文地址：http://blog.csdn.net/u013451221/article/details/44982829