4641번 Doubles

https://www.acmicpc.net/problem/4641

#include <iostream>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <cstring>
#include <string>
#include <math.h>
#include <algorithm>
#include <map>
 
using namespace std;
 
vector<int> v;
 
int search()
{
    bool visit[101] = { false, };
 
    memset(visit, false, sizeof(visit));
 
    int ret = 0;
 
    for (int i = 0; i < v.size(); i++)
    {
        int n = v.at(i);
 
        for (int j = i + 1; j < v.size(); j++)
        {
            if (2 * v.at(i) == v.at(j) || 2*v.at(j) == v.at(i))
            {
                ++ret;
            }
        }
    }
 
    return ret;
}
 
int main(void)
{
    int n = 0;
 
    while (1)
    {
        scanf("%d", &n);
 
        if (n == -1) break;
        else if (n != -1 && n != 0) v.push_back(n);
        else if (n == 0)
        {
            printf("%d\n", search());
            v.clear();
        }
    }
 
    return 0;
}