hdu 2665 Kth number（划分树）

Posted 2020-09-18 liguangsunls

Kth number

Time Limit: 15000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4602 Accepted Submission(s): 1468

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
刚学了划分树。来做这一题。仅仅知道划分树的原理，代码是自己写的，不是通用的写法。
G++AC C++超内存。。。

#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

const int maxn = 100000;
struct tree{
    int l , r;
    vector<int> element , lft;
}a[3*maxn];
vector<int> seq;
int n , m;

bool cmp(int a , int b){ return a<b;}

void build(int l , int r , int k){
    a[k].l = l;
    a[k].r = r;
    if(l != r){
        int mid = (l+r)/2;
        int lson = 2*k , rson = 2*k+1;
        a[lson].element.clear();
        a[rson].element.clear();
        a[lson].element.push_back(0);
        a[rson].element.push_back(0);
        a[lson].lft.clear();
        a[rson].lft.clear();
        a[lson].lft.push_back(0);
        a[rson].lft.push_back(0);
        for(int i = 1; i < a[k].element.size(); i++){
            if(a[k].element[i] <= seq[mid]){
                a[lson].element.push_back(a[k].element[i]);
                a[k].lft.push_back(a[k].lft[i-1]+1);
            }else{
                a[rson].element.push_back(a[k].element[i]);
                a[k].lft.push_back(a[k].lft[i-1]);
            }
        }
        build(l , mid , 2*k);
        build(mid+1 , r , 2*k+1);
    }
}

int query(int l , int r , int k , int kth){
    if(a[k].l==a[k].r){
        return a[k].element[1];
    }else{
        int tem = a[k].lft[r]-a[k].lft[l-1];
        if(tem >= kth){
            return query(1+a[k].lft[l-1] , 1+a[k].lft[l-1]+tem-1 , 2*k , kth);
        }else{
            return query(1+(l-1-a[k].lft[l-1]) , (l-1-a[k].lft[l-1])+r-l+1-tem , 2*k+1 , kth-tem);
        }
    }
}

void initial(){
    a[1].element.clear();
    a[1].element.push_back(0);
    a[1].lft.clear();
    a[1].lft.push_back(0);
    seq.clear();
}

void readcase(){
    scanf("%d%d" , &n , &m);
    seq.push_back(0);
    for(int i = 0; i < n; i++){
        int num;
        scanf("%d" , &num);
        if(seq[0] >= num) seq[0] = num-1;
        seq.push_back(num);
        a[1].element.push_back(num);
    }
}

void computing(){
    sort(seq.begin() , seq.end() , cmp);
    build(1 , n , 1);
    int s , t , k;
    while(m--){
        scanf("%d%d%d" , &s , &t , &k);
        printf("%d\n" , query(s , t , 1 , k));
    }
}

int main(){
    int t;
    scanf("%d" , &t);
    while(t--){
        initial();
        readcase();
        computing();
    }
    return 0;
}