- C++ Programming Examples
- C++ Programming Examples
- C++ Hello World
- C++ Get Input
- C++ Print Integer
- C++ Add Two Numbers
- C++ Add Sub Mul Div
- C++ Add Digits
- C++ Find Average Perc
- C++ Find Arithmetic Mean
- C++ Sum of n Natural Numbers
- C++ Sum of n Numbers
- C++ Area Perimeter of Square
- C++ Area Perimeter of Rectangle
- C++ Area Perimeter of Triangle
- C++ Area Circum of Circle
- C++ Find Simple Interest
- C++ Fahrenheit to Celsius
- C++ Celsius to Fahrenheit
- C++ Print Prime Numbers
- C++ Reverse a Number
- C++ Swap Two Numbers
- C++ Print Multiplication Table
- C++ Find Factorial of Number
- C++ Find Factors of Number
- C++ Find HCF & LCM
- C++ Make Calculator
- C++ Count Digits in Number
- C++ Sum of First & Last Digit
- C++ Product of Digits of Number
- C++ Sum of Squares of Digits
- C++ Interchange Digits of Number
- C++ if else Programs
- C++ Check Even or Odd
- C++ Check Prime or Not
- C++ Check Alphabet or Not
- C++ Check Vowel or Not
- C++ Check Leap Year or Not
- Check Reverse equal Original
- C++ Check Perfect Number
- C++ Check Palindrome or Not
- C++ Check Armstrong or Not
- C++ Divisibility Test
- C++ Find Wage of Labor
- C++ Find Discounted Price
- C++ Find Shipping Charge
- C++ Find Telephone Bills
- C++ Calculate Student Grade
- C++ Largest of Two Numbers
- C++ Largest of Three Numbers
- C++ Number Conversion
- C++ Decimal to Binary
- C++ Decimal to Octal
- C++ Decimal to Hexadecimal
- C++ Binary to Decimal
- C++ Binary to Octal
- C++ Binary to Hexadecimal
- C++ Octal to Decimal
- C++ Octal to Binary
- C++ Octal to Hexadecimal
- C++ Hexadecimal to Decimal
- C++ Hexadecimal to Binary
- C++ Hexadecimal to Octal
- C++ Pattern Programs
- C++ Pattern Programs
- C++ Print Diamond Pattern
- C++ Print Floyd's Triangle
- C++ Print Pascal's Triangle
- C++ Array Programs
- C++ 1D Array Program
- C++ Linear Search
- C++ Binary Search
- Find Largest Element in Array
- Find Smallest Element in Array
- Find Second Largest Element
- Find Second Smallest Element
- C++ Sum of All Elements
- C++ Multiply All Elements
- C++ Element on Even Position
- C++ Element on Odd Position
- C++ Print Even Numbers in Array
- C++ Print Odd Numbers in Array
- C++ Count Even/Odd Numbers
- C++ Sum of Even/Odd Numbers
- C++ Count Positive Negative Zero
- C++ Reverse an Array
- C++ Insert Element in Array
- C++ Delete Element from Array
- C++ Merge two Arrays
- C++ Bubble Sort
- C++ Selection Sort
- C++ Insertion Sort
- C++ Common Elements
- C++ 2D Array Programs
- C++ Add Two Matrices
- C++ Subtract Two Matrices
- C++ Transpose Matrix
- C++ Multiply Two Matrices
- C++ 3D Array Programs
- C++ String Programs
- C++ Print String
- C++ Find Length of String
- C++ Compare Two Strings
- C++ Copy String
- C++ Concatenate String
- C++ Reverse a String
- C++ Delete Vowels from String
- C++ Delete Word from String
- C++ Count Character in String
- C++ Count Word in String
- C++ Frequency of Word
- C++ Remove Spaces from String
- C++ Sort a String
- C++ Uppercase to Lowercase
- C++ Lowercase to Uppercase
- C++ Swap Two Strings
- C++ Check Anagram or Not
- C++ Capitalize All Words in String
- C++ Capitalize Specific Character
- C++ Get Numbers from String
- C++ File Programs
- C++ Read a File
- C++ Write Content to File
- C++ Append Data in File
- C++ Read & Display File
- C++ Copy a File
- C++ Merge Two Files
- Count Characters, Words in File
- C++ Capitalize All Words in File
- C++ List Files in Directory
- C++ Delete a File
- C++ Encrypt & Decrypt a File
- C++ Misc Programs
- C++ Print ASCII Value
- C++ Add Binary Numbers
- C++ Generate Random Numbers
- C++ Print Smiling Face
- C++ Days into Years, Months
- Add Two Numbers using Pointer
- C++ Print Fibonacci Series
- Generate Armstrong Numbers
- C++ Find nCr and nPr
- C++ Get IP Address
- C++ Print Date/Time
- C++ Shutdown, Restart Computer
- C++ Programming Tutorial
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C++ Program to Reverse a Number
In this article, you will learn and get code to reverse a number entered by user at run-time using a C++ program. Since there are many ways to create a C++ program to reverse a number, therefore we've used some famous method to do the task as given below:
- Reverse a Number using while Loop
- using for Loop
- without using Loop
- using Function
- using Class and Object
- using Array
These are the most common and popular ways to approach to reverse a given number in C++. Let's start with first way to find and print reverse of a number.
Reverse a Number using while Loop
To reverse a number in C++ programming, then you have to ask from user to enter a number. Now find the reverse of that number, and then print its reverse on output as shown in the program given below:
The question is, write a program in C++ to reverse a number. Here is its answer:
#include<iostream> using namespace std; int main() { int num, rem, rev=0; cout<<"Enter the Number: "; cin>>num; while(num!=0) { rem = num%10; rev = rem + (rev*10); num = num/10; } cout<<"\nReverse = "<<rev; cout<<endl; return 0; }
This program was build and run under Code::Blocks IDE. Here is its sample run:
Now supply the number say 123 as input, and press ENTER
key to reverse it and print as shown
in the snapshot given below:
The dry run of above program with user input 123 goes like:
- Initial value, rev=0
- When user enters the number 123, it gets stored in num
- Now the condition num!=0 (of while loop) or 123!=0 evaluates to be true, therefore program flow goes inside the loop and all the three statements gets executed
- That is, num%10 or 123%10 or 3 gets initialized to rem
- Then rem + (rev*10) or 3 + (0*10) or 3 gets initialized to rev. So rev=3
- And finally, num/10 or 123/10 or 12 gets initialized to num. So num=12
- Now after executing all the three statements of while loop, its condition again gets evaluated
- That is, the condition num!=0 or 12!=0 again evaluates to be true, therefore program flow again goes inside the loop
- Inside the loop, again num%10 or 12%10 or 2 gets initialized to rem
- Then rem + (rev*10) or 2 + (3*10) or 2+30 or 32 gets initialized to rev. So rev=32
- num/10 or 12/10 or 1 gets initialized to num. So num=1
- Again the condition of while loop gets evaluated. That is, num!=0 or 1!=0 evaluates to be true, therefore all the three statements gets executed
- That is, num%10 or 1%10 or 1 gets initialized to rem. And rem + (rev*10) or 1 + (32*10) or 1+320 or 321 gets initialized to rev. Finally num/10 or 1/10 or 0 gets initialized to num. So after executing all the three statements, we've rev=321 and num=0
- Now this time, the condition (of while loop) num!=0 or 0!=0 evaluates to be false. Therefore the evaluation of while loop gets ended
- Now we've a variable rev, that holds the reverse (321) of given number (123)
- So just print the value of rev as reverse of a number entered by user at run-time
Reverse a Number using for Loop
This program is created using for loop, instead of while loop. Rest of the things are same as of previous program:
#include<iostream> using namespace std; int main() { int num, rem, rev; cout<<"Enter the Number: "; cin>>num; for(rev=0; num!=0; num=num/10) { rem = num%10; rev = rem + (rev*10); } cout<<"\nReverse = "<<rev; cout<<endl; return 0; }
Here is its sample run with user input, 23056:
Reverse a Number without using Loop
This program doesn't use any type of loop, neither for nor while loop to reverse a number. Let's have a look at the program first, its explanation is given later on:
#include<iostream> using namespace std; int main() { int num, rem, rev=0; cout<<"Enter the Number: "; cin>>num; CODESCRACKER: rem = num%10; rev = (rev*10) + rem; num = num/10; if(num!=0) goto CODESCRACKER; cout<<"\nReverse = "<<rev; cout<<endl; return 0; }
This program produces the same output as of previous program.
Note - A label named CODESCRACKER is created, where all the three statements of reversing a number is written. After executing all the three statements, we've used if for the condition (to check) as done in while loop. That is, if the condition evaluates to be true, therefore using goto keyword followed by label name, program flow start from the label again.
Reverse a Number using Function
This program uses a user-defined function named rev() to reverse a number. It takes a number as its argument, and returns its reverse.
#include<iostream> using namespace std; int rev(int); int main() { int num, r; cout<<"Enter the Number: "; cin>>num; r = rev(num); cout<<"\nReverse = "<<r; cout<<endl; return 0; } int rev(int n) { int rem, res=0; while(n!=0) { rem = n%10; res = (res*10) + rem; n = n/10; } return res; }
Reverse a Number using Class
This program uses class and object, an object-oriented feature of C++ to reverse a number given by user:
#include<iostream> using namespace std; class CodesCracker { public: int rev(int); }; int CodesCracker::rev(int n) { int rem, res=0; while(n!=0) { rem = n%10; res = (res*10) + rem; n = n/10; } return res; } int main() { int num, r; CodesCracker c; cout<<"Enter the Number: "; cin>>num; r = c.rev(num); cout<<"\nReverse = "<<r; cout<<endl; return 0; }
Note - An object c of type CodesCracker is created inside the main() function. Now using the object c we've called the member function of the class CodesCracker just like normal function calling using dot (.) operator. The function rev() also returns reverse of a number that is passed as its argument, just like the previous program of normal function.
Reverse a Number using Array
This is the last program on reversing of a number. This program is created using an array. That is, each digit of the number gets initialized as elements of array. And using array, we've printed the reverse of given number:
#include<iostream> using namespace std; int main() { int num, rem, arr[10], i=0, tot=0; cout<<"Enter the Number: "; cin>>num; while(num!=0) { rem = num%10; arr[i] = rem; num = num/10; i++; tot++; } cout<<"\nReverse = "; for(i=0; i<tot; i++) cout<<arr[i]; cout<<endl; return 0; }
Same Program in Other Languages
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