C Exercises: Reverse the digits of a given integer

Last update on December 20 2024 13:18:58 (UTC/GMT +8 hours)

Write a C program to reverse the digits of a given integer.

Example:
Input:
i = 123
i = 208478933
i = -73634
Output:
Reverse integer: 321
Reverse integer: 339874802
Reverse integer: -43637

Visual Presentation:

Sample Solution:

C Code:

#include <stdio.h>

// Function to reverse the digits of an integer
int reverse(int n) {
    int d, y = 0;

    // Reversing the digits of the integer
    while (n) {
        d = n % 10;

        // Check for potential overflow before updating the reversed integer
        if ((n > 0 && y > (0x7fffffff - d) / 10) ||
            (n < 0 && y < ((signed)0x80000000 - d) / 10)) {
            return 0;  // Return 0 if overflow detected
        }

        y = y * 10 + d;  // Update the reversed integer
        n = n / 10;      // Move to the next digit
    }

    return y;  // Return the reversed integer
}

int main(void)
{
    int i = 123;
    printf("Original integer: %d  ", i);
    printf("\nReverse integer: %d  ", reverse(i));

    i = 208478933;
    printf("\nOriginal integer: %d  ", i);
    printf("\nReverse integer: %d  ", reverse(i));

    i = -73634;
    printf("\nOriginal integer: %d  ", i);
    printf("\nReverse integer: %d  ", reverse(i));

    return 0;
}

Sample Output:

Original integer: 123  
Reverse integer: 321  
Original integer: 208478933  
Reverse integer: 339874802  
Original integer: -73634  
Reverse integer: -43637  

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