Print prime factors of a given integer in decreasing order using Stack

Given an integer N, the task is to print prime factors of N in decreasing order using the stack data structure.

Examples:

Input: N = 34
Output:
17 2
Explanation:
The prime factors of the number 34 is 2 and 17.

Input: N = 8
Output: 2

Approach: The idea is to use the Stack data structure to store all the prime factors of N and in the end, print all the values in the Stack. Follow the steps below to solve the problem:

1. Initialize a stack, say st.
2. Run a loop while N != 1. From i = 2, for each value of i, run a loop until N % i == 0 and push i into the stack st and update N to N/i.
3. Finally, print all the values from top to bottom of stack st.

Below is the implementation of the above approach:

C++

// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to print prime factors
// of N in decreasing order
void PrimeFactors(int N)
{
    // Stores prime factors of N
    // in decreasing order
    stack<int> st;

    int i = 2;
    while (N != 1) {

        if (N % i == 0) {

            // Insert i into stack
            st.push(i);

            while (N % i == 0) {

                // Update N
                N = N / i;
            }
        }

        // Update i
        i++;
    }

    // Print value of stack st
    while (!st.empty()) {

        printf("%d ", st.top());
        st.pop();
    }
}

// Driver Code
int main()
{
    int N = 8;

    // function Call
    PrimeFactors(N);
    return 0;
}

Java

// Java program for the above approach
import java.util.*;

class GFG{

// Function to print prime factors
// of N in decreasing order
static void PrimeFactors(int N)
{

    // Stores prime factors of N
    // in decreasing order
    Stack<Integer> st = new Stack<>();

    int i = 2;

    while (N != 1)
    {
        if (N % i == 0)
        {

            // Insert i into stack
            st.push(i);

            while (N % i == 0)
            {

                // Update N
                N = N / i;
            }
        }

        // Update i
        i++;
    }

    // Print value of stack st
    while (!st.isEmpty())
    {
        System.out.println(st.peek());
        st.pop();
    }
}

// Driver Code
public static void main (String[] args)
{
    int N = 8;

    // Function Call
    PrimeFactors(N);;
}
}

// This code is contributed by susmitakundugoaldanga

Python3

# Python3 program for the above approach

# Function to print prime factors
# of N in decreasing order
def PrimeFactors(N):

    # Stores prime factors of N
    # in decreasing order
    st = []
    i = 2
    while (N != 1):
        if (N % i == 0):

            # Insert i into stack
            st.append(i)
            while (N % i == 0):

                # Update N
                N = N // i

        # Update i
        i += 1

    # Print value of stack st
    while (len(st) != 0):
        print(st[-1])
        st.pop()

# Driver Code
if __name__ == "__main__":
    N = 8

    # function Call
    PrimeFactors(N)

    # This code is contributed by chitranayal.

C#

// C# program for the above approach
using System;
using System.Collections.Generic;

class GFG{

// Function to print prime factors
// of N in decreasing order
static void PrimeFactors(int N)
{

    // Stores prime factors of N
    // in decreasing order
    Stack<int> st = new Stack<int>();

    int i = 2;

    while (N != 1)
    {
        if (N % i == 0)
        {

            // Insert i into stack
            st.Push(i);

            while (N % i == 0)
            {

                // Update N
                N = N / i;
            }
        }

        // Update i
        i++;
    }

    // Print value of stack st
    while (st.Count != 0)
    {
        Console.Write(st.Peek());
        st.Pop();
    }
}

// Driver Code
public static void Main ()
{
    int N = 8;

    // Function Call
    PrimeFactors(N);;
}
}

// This code is contributed by code_hunt

Javascript

<script>

// JavaScript program for the above approach

// Function to print prime factors
// of N in decreasing order
function PrimeFactors(N)
{
    // Stores prime factors of N
    // in decreasing order
    let st = [];

    let i = 2;

    while (N != 1)
    {
        if (N % i == 0)
        {

            // Insert i into stack
            st.push(i);

            while (N % i == 0)
            {

                // Update N
                N = Math.floor(N / i);
            }
        }

        // Update i
        i++;
    }

    // Print value of stack st
    while (st.length!=0)
    {
        document.write(st.pop());

    }
}
// Driver Code
let N = 8;

// Function Call
PrimeFactors(N);


// This code is contributed by avanitrachhadiya2155

</script>

Output:

2

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