Given a number , write a program to reverse this number using stack.
Examples:
Input : 365 Output : 563 Input : 6899 Output : 9986
We have already discussed the simple method to reverse a number in this post. In this post we will discuss about how to reverse a number using stack.
The idea to do this is to extract digits of the number and push the digits on to a stack. Once all of the digits of the number are pushed to the stack, we will start poping the contents of stack one by one and form a number.
As stack is a LIFO data structure, digits of the newly formed number will be in reverse order.
Below is the implementation of above idea:
C++
// CPP program to reverse the number // using a stack #include <bits/stdc++.h>using namespace std; // Stack to maintain order of digitsstack <int> st; // Function to push digits into stackvoid push_digits(int number){ while (number != 0) { st.push(number % 10); number = number / 10; }} // Function to reverse the numberint reverse_number(int number){ // Function call to push number's // digits to stack push_digits(number); int reverse = 0; int i = 1; // Popping the digits and forming // the reversed number while (!st.empty()) { reverse = reverse + (st.top() * i); st.pop(); i = i * 10; } // Return the reversed number formed return reverse;} // Driver program to test above functionint main(){ int number = 39997; // Function call to reverse number cout << reverse_number(number); return 0;} |
Java
// Java program to reverse the number// using a stackimport java.util.Stack; public class GFG{ // Stack to maintain order of digits static Stack<Integer> st= new Stack<>(); // Function to push digits into stack static void push_digits(int number) { while(number != 0) { st.push(number % 10); number = number / 10; } } // Function to reverse the number static int reverse_number(int number) { // Function call to push number's // digits to stack push_digits(number); int reverse = 0; int i = 1; // Popping the digits and forming // the reversed number while (!st.isEmpty()) { reverse = reverse + (st.peek() * i); st.pop(); i = i * 10; } // Return the reversed number formed return reverse; } // Driver program to test above function public static void main(String[] args) { int number = 39997; System.out.println(reverse_number(number)); }}// This code is contributed by Sumit Ghosh |
Python3
# Python3 program to reverse the # number using a stack # Stack to maintain order of digitsst = []; # Function to push digits into stackdef push_digits(number): while (number != 0): st.append(number % 10); number = int(number / 10); # Function to reverse the numberdef reverse_number(number): # Function call to push number's # digits to stack push_digits(number); reverse = 0; i = 1; # Popping the digits and forming # the reversed number while (len(st) > 0): reverse = reverse + (st[len(st) - 1] * i); st.pop(); i = i * 10; # Return the reversed number formed return reverse; # Driver Codenumber = 39997; # Function call to reverse numberprint(reverse_number(number)); # This code is contributed by mits |
C#
// C# program to reverse the number // using a stack using System;using System.Collections.Generic; class GFG{// Stack to maintain order of digits public static Stack<int> st = new Stack<int>(); // Function to push digits into stack public static void push_digits(int number){ while (number != 0) { st.Push(number % 10); number = number / 10; }} // Function to reverse the number public static int reverse_number(int number){ // Function call to push number's // digits to stack push_digits(number); int reverse = 0; int i = 1; // Popping the digits and forming // the reversed number while (st.Count > 0) { reverse = reverse + (st.Peek() * i); st.Pop(); i = i * 10; } // Return the reversed number formed return reverse;} // Driver Codepublic static void Main(string[] args){ int number = 39997; Console.WriteLine(reverse_number(number));}} // This code is contributed by Shrikant13 |
PHP
<?php// PHP program to reverse the number // using a stack // Stack to maintain order of digits$st = array(); // Function to push digits into stackfunction push_digits($number){ global $st; while ($number != 0) { array_push($st, $number % 10); $number = (int)($number / 10); }} // Function to reverse the numberfunction reverse_number($number){ global $st; // Function call to push number's // digits to stack push_digits($number); $reverse = 0; $i = 1; // Popping the digits and forming // the reversed number while (!empty($st)) { $reverse = $reverse + ($st[count($st) - 1] * $i); array_pop($st); $i = $i * 10; } // Return the reversed number formed return $reverse;} // Driver Code$number = 39997; // Function call to reverse numberecho reverse_number($number); // This code is contributed by mits?> |
Output:
79993
Time Complexity: O( logN )
Auxiliary Space: O( logN ), Where N is the input number.
This article is contributed by Rohit Thapliyal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
