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Make two numbers equal in at most K steps dividing by their factor

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  • Difficulty Level : Hard
  • Last Updated : 21 Jul, 2022

Given integers X, Y, and K, the task is to make X and Y equal in not more than K operations by applying the following operations:

  • Choose an integer A and make X = X/A, (where A is an integer that is greater than 1 and not equal to X).
  • Choose an integer A and make Y = Y/A, (where A is an integer that is greater than 1 and not equal to Y).

Examples:

Input: X = 10, Y = 20, K = 4
Output: YES
Explanation: One optimal solution to make them equal is:
First choose A = 2 and do X = X/2 so now X is equal to 5.
Now choose A = 4 and do Y = Y/4 so now Y is equal to 5.
Since we have applied only two operations here which is less than K 
to make X and Y equal and also greater than one.
Therefore the answer is YES.

Input: X = 2, Y = 27, K = 1
Output: NO
Explanation: There is no possible way to make X and Y equal 
in less than or equal to 1 Operation.

 

Approach: To solve the problem follow the below idea:

Here are only two cases possible:

  • When K is equal to one and 
  • When K is greater than 1

If K is equal to one then it is possible to make X and Y equal only when either X is divisible by Y or Y is divisible by X

If K is greater than 1 then X and Y can be equal and greater than 1 only when their GCD is greater than 1.

Follow the steps mentioned below to implement the idea:

  • Check if K = 1:
    • In that case, find out if any of them is a divisor of the other.
  • Otherwise, find the GCD of the numbers.
    • If the GCD is 1 then it is not possible.
    • Otherwise, an answer always exists.

Below is the implementation for the above approach:

C++




// C++ code to implement the approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to check the possibility of the answer
bool isPossible(int X, int Y, int K)
{
    // Case 1: when k=1
    if (K == 1) {
        if (X % Y == 0 || Y % X == 0)
            return true;
        return false;
    }
 
    // Case 2: when k>1
    else {
        if (__gcd(X, Y) > 1)
            return true;
        return false;
    }
    return false;
}
 
// Driver code
int main()
{
    int X = 10;
    int Y = 20;
    int K = 4;
 
    // Function call
    bool answer = isPossible(X, Y, K);
    if (answer)
        cout << "YES";
    else
        cout << "NO";
    return 0;
}


Java




// Java code to implement the approach
 
public class GFG {
     
   // Recursive function to return gcd of a and b
    static int gcd(int a, int b)
    {
        // Everything divides 0
        if (a == 0)
          return b;
        if (b == 0)
          return a;
       
        // base case
        if (a == b)
            return a;
       
        // a is greater
        if (a > b)
            return gcd(a-b, b);
        return gcd(a, b-a);
    }
     
    // Function to check the possibility of the answer
    static boolean isPossible(int X, int Y, int K)
    {
        // Case 1: when k=1
        if (K == 1) {
            if (X % Y == 0 || Y % X == 0)
                return true;
            return false;
        }
     
        // Case 2: when k>1
        else {
            if (gcd(X, Y) > 1)
                return true;
            return false;
        }
    }
     
    // Driver code
    public static void main (String[] args)
    {
        int X = 10;
        int Y = 20;
        int K = 4;
     
        // Function call
        boolean answer = isPossible(X, Y, K);
        if (answer == true)
            System.out.println("YES");
        else
            System.out.println("NO");
    }
}
 
// This code is contributed by AnkThon


Python3




# Python3 code to implement the approach
import math
 
# Function to check the possibility of the answer
def isPossible(X, Y, K):
     
    # Case 1: when k=1
    if (K == 1) :
        return (X % Y == 0 or Y % X == 0)
 
    # Case 2: when k>1
    else :
        return (math.gcd(X, Y) > 1)
 
    return False
 
# Driver code
X, Y, K = 10, 20, 4
 
# Function call
answer = isPossible(X, Y, K);
 
if (answer):
    print("YES")
else:
    print("NO")
 
# This code is contributed by phasing17


C#




// C# code to implement the approach
using System;
 
public class GFG {
     
   // Recursive function to return gcd of a and b
    static int gcd(int a, int b)
    {
        // Everything divides 0
        if (a == 0)
          return b;
        if (b == 0)
          return a;
       
        // base case
        if (a == b)
            return a;
       
        // a is greater
        if (a > b)
            return gcd(a-b, b);
        return gcd(a, b-a);
    }
     
    // Function to check the possibility of the answer
    static bool isPossible(int X, int Y, int K)
    {
        // Case 1: when k=1
        if (K == 1) {
            if (X % Y == 0 || Y % X == 0)
                return true;
            return false;
        }
     
        // Case 2: when k>1
        else {
            if (gcd(X, Y) > 1)
                return true;
            return false;
        }
    }
     
    // Driver code
    public static void Main (string[] args)
    {
        int X = 10;
        int Y = 20;
        int K = 4;
     
        // Function call
        bool answer = isPossible(X, Y, K);
        if (answer == true)
            Console.WriteLine("YES");
        else
            Console.WriteLine("NO");
    }
}
 
// This code is contributed by AnkThon


Javascript




<script>
//Javascript code to implement the approach
function _gcd(a,b){
   if(b==0)
     return a;
     return _gcd(b,a%b);
}
 
// Function to check the possibility of the answer
function isPossible(X, Y, K)
{
    // Case 1: when k=1
    if (K == 1) {
        if (X % Y == 0 || Y % X == 0)
            return true;
        return false;
    }
 
    // Case 2: when k>1
    else {
        if (_gcd(X, Y) > 1)
            return true;
        return false;
    }
    return false;
}
 
// Driver code
 
    let X = 10;
    let Y = 20;
    let K = 4;
 
    // Function call
    let answer = isPossible(X, Y, K);
    if (answer)
        document.write("YES","</br>")
    else
        document.write("NO","</br>")
         
        // This code is contributed by satwik4409.
    </script>


Output

YES

Time Complexity: O(1)
Auxiliary Space: O(1)


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