Question

How to find whether an array include a pair of which product equals to N in C++

Answer 1

#include <iostream>
#include <unordered_set>
 
bool ProductExists(int arr[], int size, int N) {
    if (size < 2)
        return false;
     
    std::unordered_set<int> set;
   
    for (int i = 0; i < size; i++) {
        if (arr[i] == 0 && N == 0)  {
            return true;
        }
        if (N % arr[i] == 0) {
            if (set.find(N / arr[i]) != set.end())
                return true;
            set.insert(arr[i]);
        }
    }
       
    return false;
}
 
int main()
{
    int arr[] = {5, 7, 13, 25, 9, 3, 4};
    int size = sizeof(arr) / sizeof(arr[0]);
    int N = 21;
 
    std::cout << (ProductExists(arr, size, N) ? "Yes" : "No");
}
 
 
 
 
/*
run:
 
Yes
 
*/

 

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