C Exercises: Find next smallest palindrome of a given number

Last update on March 20 2025 12:35:32 (UTC/GMT +8 hours)

23. Next Smallest Palindrome Variants

Write a C program to find next smallest palindrome of a given number.

From Wikipedia,
A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as madam, racecar. There are also numeric palindromes, including date/time stamps using short digits 11/11/11 11:11 and long digits 02/02/2020. Sentence-length palindromes may be written when allowances are made for adjustments to capital letters, punctuation, and word dividers, such as "A man, a plan, a canal, Panama!".

Example:
Input: n = 121
Output: Next smallest palindrome of 121 is 131

Visual Presentation:

Sample Solution:

C Code:

#include <stdio.h>
#include <stdlib.h>

// Function to generate the next smallest palindrome after 'n'
int nextPalindromeGenerate(int n)
{   
    int ans=1, digit, rev_num=0, num; // Declare variables ans, digit, rev_num, and num              
    if(n<10) // Check if n is less than 10
    {   
        ans=0; // Set ans to 0
        return n+1; // Return n+1 as the next smallest palindrome
    }
    num=n; // Store the original value of n
    while(ans!=0) // While loop until ans is not 0
    {   
        rev_num=0; // Initialize rev_num to 0
        digit=0; // Initialize digit to 0
        n=++num; // Increment num and assign to n

        while(n>0) // While loop to reverse the number and store it in rev_num       
        {
            digit=n%10; // Get the last digit of n
            rev_num=rev_num*10+digit; // Append digit to rev_num
            n=n/10; // Remove the last digit from n
        }
        if(rev_num==num) // Check if the reversed number is equal to the original number   
        {
            ans=0; // Set ans to 0
            return num; // Return the palindrome number
        }
        else 
            ans=1; // Set ans to 1 to continue the loop
    }
    return num; // Return the next palindrome number
}

int main(void)
{          
    int n = 121; // Declare and initialize n to 121
    if (n>0); // Check if n is positive (semicolon here may cause unexpected behavior, it's better to remove it)
    {	
        printf("Next smallest palindrome of %d is %d", n, nextPalindromeGenerate(n)); // Print the next smallest palindrome of n
    }         
    return 0; // Return 0 to indicate successful execution
}

Sample Output:

Next smallest palindrome of 121 is 131

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to find the next palindrome greater than a given integer using digit manipulation.
• Write a C program to compute the next smallest palindrome by mirroring the first half of the number.
• Write a C program to determine the next palindrome by incrementing and checking until a valid palindrome is found.
• Write a C program to generate the next palindrome with edge case handling for numbers like 9, 99, etc.

C Programming Code Editor:

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