Write a program that takes an integer as input and reverses its digits.
Input/Output Examples
plaintext
Input: 1234
Output: 4321
Input: -123
Output: -321
Algorithm to reverse a number
- Start
- Read the input number.
- Initialize a variable to store the reverse number (initially 0).
- Extract the last digit of the given number by taking the modulo by 10.
- Multiply the reverse number by 10 and add the last digit to it.
- Divide the original number by 10.
- Repeat steps 4-6 until the number becomes 0.
- If the original number was negative, make the reverse number negative.
- Print the reverse number.
- End
C++ Program to reverse a number
cpp
#include <iostream>
using namespace std;
int main() {
int num, reverseNum = 0, digit;
// Prompt user for number input
cout << "Enter an integer: ";
// Read the number
cin >> num;
// Store original number to check if it's negative later
int originalNum = num;
// Loop until num becomes 0
while (num != 0) {
// Extract the last digit
digit = num % 10;
// Construct the reverse number
reverseNum = reverseNum * 10 + digit;
// Remove the last digit from num
num /= 10;
}
// Check if original number was negative
if (originalNum < 0) {
// Make the reverse number negative
reverseNum = -reverseNum;
}
// Print the reverse number
cout << "Reversed Number: " << reverseNum;
return 0;
}
Java Program to reverse a number
java
import java.util.Scanner;
public class ReverseNumber {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
// Prompt user for number input
System.out.print("Enter an integer: ");
// Read the number
int num = scanner.nextInt();
int originalNum = num; // Store original number
int reverseNum = 0; // Variable to store the reverse of the number
// Loop until num becomes 0
while (num != 0) {
// Extract the last digit and update reverseNum
reverseNum = reverseNum * 10 + num % 10;
// Remove the last digit from num
num /= 10;
}
// If the original number was negative, make the reversed number negative
if (originalNum < 0) {
reverseNum = -reverseNum;
}
// Print the reversed number
System.out.println("Reversed Number: " + reverseNum);
}
}
Python Program to reverse a number
python
# Get the number from the user
num = int(input("Enter an integer: "))
originalNum = num # Store original number to check negativity
reverseNum = 0 # Variable to store the reverse of the number
# Loop until num becomes 0
while num != 0:
# Extract the last digit and update reverseNum
reverseNum = reverseNum * 10 + num % 10
# Remove the last digit from num
num = int(num / 10) # Use int for floor division in Python 3
# If the original number was negative, make the reversed number negative
if originalNum < 0:
reverseNum = -reverseNum
# Print the reversed number
print("Reversed Number:", reverseNum)
