C Program to Find Reverse of a Number

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Conditional Operator
While loop in C
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For loop in C
Break keyword in C
Continue keyword in C
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Find GCD and LCM
Find factorial of Number
Count Number of Digits
Sum of digits in Number
Sum of N Natural Numbers
Sum of Squares of Natural No.
Find Sum of Odd Numbers
Find the Sum of Series
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Sum of the Fibonacci series
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Sum of max 10 no. & Skip -ve
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Pattern programs in C
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Floyd’s triangle Program
Pascal Triangle Program
Pyramid Star Pattern in C
Diamond Pattern Programs
Half Diamond pattern in C
Print Diamond Pattern
Hollow Diamond Pattern
Diamond Pattern of Numbers

Write a C program to find the reverse of a number. For example, the reverse of number 7854 is given as 4587.

From the operators topic, we know that the modulus operator (%) can be used to find the last digit of the number. Similarly, the division operator (/) can be used to remove the last digit of the number.

Steps to reverse a number,

Declare a variable reverse, and initialize it with 0.
Step1:- Find the last digit of the number. lastDigit = number%10
Step2:- Append this lastDigit to the variable reverse. reverse = (reverse*10)+lastdigit;
Step3:- Remove the last digit of the number. number = number/10
Repeat this process (from step1 to step3) until the number becomes 0.

C Program to Find Reverse of a Number using while loop

 #include<stdio.h>
 int main()
 {
     int number, lastDigit, reverse=0;

     printf("Enter a number: ");
     scanf("%d",&number);

     while( number!=0 )
     {
         lastDigit = number%10;
         reverse = (reverse*10) + lastDigit;
         number /= 10;
     }

     printf("Reverse Number = %d\n",reverse);

     return 0;
 }

Output:-

Enter a number: 12345
Reverse Number = 54321

Enter a number: 0032
Reverse Number = 23

Enter a number: 123000
Reverse Number = 321

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In this program, the input number is stored in the variable number. To reverse the number modulus and division operators are used, and the result is stored in the variable reverse.

Another Way

This method is a shortcut way and it can’t be used with big programs. Thi method after finding the last digit, it is displayed to the screen without storing it. Each iteration display one digit. The below program displays the number in reverse. Don’t use this method in another program.

 #include<stdio.h>
 int main()
 {
     int number, lastDigit;

     printf("Enter a number: ");
     scanf("%d",&number);

     while( number!=0 )
     {
         lastDigit = number%10;
         //displaying within while loop
         printf("%d",lastDigit); 
         number /= 10;
     }

     return 0;
 }

Output for different test-cases:-

Enter a number: 852
258

Enter a number: 123000
000321

Enter a number: 000032
23

C Program to Find Reverse of a Number using the do-while loop

 #include<stdio.h>
 int main()
 {
     int number, lastDigit, reverse=0;

     printf("Enter a number: ");
     scanf("%d",&number);

     do
     {
         lastDigit = number%10;
         reverse = (reverse*10) + lastDigit;
         number /= 10;
     }while( number!=0 );

     printf("Reverse Number = %d\n",reverse);

     return 0;
 }

C Program to Find Reverse of a Number using for loop

 #include<stdio.h>
 int main()
 {
     int number, lastDigit, reverse;

     printf("Enter a number: ");
     scanf("%d",&number);

     for(reverse=0; number!=0; number /= 10)
     {
         lastDigit = number%10;
         reverse = (reverse*10) + lastDigit;
     }

     printf("Reverse Number = %d\n",reverse);

     return 0;
 }

In this program reverse variable is declare before for loop becomes it is used outside of the for loop (in the last statement). If we declare the reverse variable at the time of initialization of for loop then the variable becomes local variable and can be accessed only within the for loop. You can read more about it in Scope and lifetime of a variable.

Output for the different test-cases:-

Enter a number: 12345
Reverse Number = 54321

Enter a number: 00123
Reverse Number = 321

Enter a number: 2145000
Reverse Number = 5412

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Flow Control
If-else Statement in C
Programs on if-else
Switch Case in C
Switch case Programs
Conditional Operator
While loop in C
Do-while loop in C
While vs do-while
For loop in C
Break keyword in C
Continue keyword in C
Break vs Exit in C
Goto keyword in C
☕️ Flow Control Programs
Largest among 3 Numbers
Find Grade of student
Find the absolute value
Check Vowel or Consonant
Leap Year Program
Simple calculator in C
Check Odd or Even 
Roots of Quadratic Equation
Find Reverse of Number
Factors of a number in C
Generate Multiplication table
Find Power of a Number
Find GCD and LCM
Find factorial of Number
Count Number of Digits
Sum of digits in Number
Sum of N Natural Numbers
Sum of Squares of Natural No.
Find Sum of Odd Numbers
Find the Sum of Series
Find Fibonacci series in C
Sum of the Fibonacci series
Sum until enters +ve numbers
Sum of max 10 no. & Skip -ve
☕️ C Conversion Programs
Celsius to Fahrenheit
Fahrenheit to Celsius
Decimal ↔ Binary
Decimal ↔ Octal
Octal ↔ Binary in C
☕️ Number Programs in C
Prime Number in C
Strong Number in C
Krishnamurthy Number
Neon Number in C
Palindrome number
Perfect Number in C
Armstrong Number
☕️ Pattern Programs in C
Pattern programs in C
Printing pattern using loops
Floyd’s triangle Program
Pascal Triangle Program
Pyramid Star Pattern in C
Diamond Pattern Programs
Half Diamond pattern in C
Print Diamond Pattern
Hollow Diamond Pattern
Diamond Pattern of Numbers
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