Count number of triplets with product equal to given number in C++

We are given an array Arr[] of integers with length n and a number M. The array is only containing positive integers. The goal is to count the triplets of elements of Arr[] which have product equal to M.

We will do this by using three for loops. Increment count if arr[x]*arr[y]*arr[z]=M and x!=y!=z. (0<= x,y,z

Let’s understand with examples.

Input 

arr[]= { 1,2,3,0,2,4 }, M=24

Output 

Number of triplets with product M: 2

Explanation 

Triplets with arr[x]*arr[y]*arr[z]==M.
Arr{}=[ 1,2,3,0,2,4 ] =(2,3,4) → 2*3*4=24
Arr{}=[ 1,2,3,0,2,4 ] =(3,2,4) → 3*2*4=24
Total triplets: 2

Input 

arr[]= {2,2,2,2,2}, M=6

Output 

Number of triplets with product M: 0

Explanation 

Every triplet has product equal to 8
Total triplets: 0

Approach used in the below program is as follows

• We take an integer array Arr[] initialized with random numbers.

• Variable N stores the length of Arr[].

• Function productisM(int arr[],int n,int m) takes an array, its length returns the triplets in which product is equal to m.

• Take the initial variable count as 0 for the number of triplets.

• Traverse array using three for loops for each element of the triplet.

• Outermost loop from 0<=i<n-2, inner loop i<j<n-1, innermost j<k<n.

• Check if arr[i]*arr[j]*arr[k]==m . If true then increment count.

• At the end of all loops count will have a total number of triplets that meet the condition.

• Return the count as result.

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
int productisM(int arr[], int n, int m){
   int count = 0;
   for (int i = 0; i < n-2; i++){
      for (int j = i+1; j < n-1; j++){
         for (int k = j+1; k < n; k++){
            int prod=arr[i]*arr[j]*arr[k];
            if(prod==m)
               { count++; }
         }
      }
   }
   return count;
}
int main(){
   int Arr[]={ 1,2,3,0,2,4 };
   int N=6; //length of array
   int M=24;
   cout <<endl<< "Number of triplets with product M : "<<productisM(Arr,N,M);
   return 0;
}

Output

If we run the above code it will generate the following output −

Number of triplets with product M: 4