Binary Search (Hackerearth)

gist.cpp

#include <vector>
#include <algorithm>
#include <iostream>

// Write your code here
int binary_search(const std::vector<int> &a, int e) 
{ 
    int l = 0;
    int r = a.size() - 1;
    
    while (l <= r) { 
        int m = l + (r - l) / 2; 
        if (a[m] == e) 
            return m + 1; 
        if (a[m] < e) 
            l = m + 1; 
        else
            r = m - 1; 
    }
    
    return -1; 
} 

// output to a
void read_array(int n, std::vector<int> &a)
{
    int e;
    int count = 0;
    while(count < n) {
        std::cin >> e;
        a.push_back(e);
        count += 1;
    }
}

int main()
{
    int n;
    int q;
    
    std::cin >> n;
    std::vector<int> a;
    read_array(n, a);
    
    std::cin >> q;
    std::vector<int> queries;
    read_array(q, queries);
    
    std::sort(a.begin(), a.end());
    
    for(auto e : queries) {
        std::cout << binary_search(a, e) << std::endl;
    }

    return 0;
}