HDU-2665 Kth number

Kth number

Time Limit: 15000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 12578    Accepted Submission(s): 3831

Problem Description

Give you a sequence and ask you the kth big number of a inteval.

 

Input

The first line is the number of the test cases. 
For each test case, the first line contain two integer n and m (n, m <= 100000), indicates the number of integers in the sequence and the number of the quaere. 
The second line contains n integers, describe the sequence. 
Each of following m lines contains three integers s, t, k. 
[s, t] indicates the interval and k indicates the kth big number in interval [s, t]

 

Output

For each test case, output m lines. Each line contains the kth big number.

 

Sample Input

1 
10 1 
1 4 2 3 5 6 7 8 9 0 
1 3 2 

 

Sample Output

2

题目大意：就是寻找第k大的数，无修改，主席树模板测试题

#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define lson l,m
#define rson m+1,r
const int N=1e5+5;
int L[N<<5],R[N<<5],sum[N<<5];
int tot;
int a[N],T[N],Hash[N];

int build(int l,int r)
{
        int rt=(++tot);
        sum[rt]=0;
        if(l<r)
        {
            int m=(l+r)>>1;
            L[rt]=build(lson);
            R[rt]=build(rson);
        }
        return rt;
}

int update(int pre,int l,int r,int x)
{
    int rt=(++tot);
    L[rt]=L[pre],R[rt]=R[pre],sum[rt]=sum[pre]+1;
    if(l<r)
    {
        int m=(l+r)>>1;
        if(x<=m)
            L[rt]=update(L[pre],lson,x);
        else
            R[rt]=update(R[pre],rson,x);
    }
    return rt;
}

int query(int u,int v,int l,int r,int k)
{
    if(l>=r)
        return l;
    int m=(l+r)>>1;
    int num=sum[L[v]]-sum[L[u]];
    if(num>=k)
        return query(L[u],L[v],lson,k);
    else
        return query(R[u],R[v],rson,k-num);
}

int main()
{
    int t;
    cin>>t;
    while(t--){
        tot=0;
        int n,m;
        scanf("%d%d",&n,&m);
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
            Hash[i]=a[i];
        }
        sort(Hash+1,Hash+1+n);
        int d=unique(Hash+1,Hash+1+n)-Hash-1;
        T[0]=build(1,d);
        for(int i=1;i<=n;i++)
        {
            int x=lower_bound(Hash+1,Hash+1+d,a[i])-Hash;
            T[i]=update(T[i-1],1,d,x);
        }
        while(m--)
        {
            int l,r,k;
            scanf("%d%d%d",&l,&r,&k);
            int x=query(T[l-1],T[r],1,d,k);
            printf("%d\n",Hash[x]);
        }
    }
    //cout << "Hello world!" << endl;
    return 0;
}