C Exercises: Check whether a number is Lychrel number or not

Last update on December 20 2024 13:19:39 (UTC/GMT +8 hours)

Write a program in C to check whether a number is a Lychrel number or not.

Test Data
Input a number: 196

Sample Solution:

C Code:

#include <stdio.h> // Include standard input-output library
#include <stdbool.h> // Include library for boolean type
#include <stdlib.h> // Include standard library

// Function to check if a number is a palindrome

// Function prototypes
bool palindrome(unsigned long long int i); // Function to check if a number is a palindrome
unsigned long long int reverse(unsigned long long int i); // Function to reverse a number
bool lychrel(unsigned long long int i); // Function to check if a number is a Lychrel number

int main(void) {
    unsigned long long int i = 0; // Declare and initialize variable for input number
    int count = 0, num1; // Declare variables for count and input number
    printf("\n\n Check whether a given number is a Lychrel number or not: \n"); // Print message
    printf(" -------------------------------------------------------------\n"); // Print separator
    printf(" Input a number: "); // Prompt user for input
    scanf("%d", &num1); // Read input from user
    if (lychrel(num1)) { // Check if the input number is a Lychrel number
        printf(" The given number is Lychrel.\n\n"); // Print message if the number is a Lychrel number
    } else {
        printf(" The given number is not Lychrel.\n\n"); // Print message if the number is not a Lychrel number
    }
    return 0; // Return 0 to indicate successful execution
}

// Function to check if a number is a Lychrel number
bool lychrel(unsigned long long int i) {
    int j; // Declare variable for iteration counter
    bool lychrel = true; // Initialize variable to store Lychrel property
    i = i + reverse(i); // Add the input number to its reverse
    for (j = 1; j <= 30; j++) { // Loop up to 30 iterations
        if (palindrome(i)) { // Check if the result is a palindrome
            lychrel = false; // If palindrome found, set lychrel to false
            break; // Exit the loop
        }
        i = i + reverse(i); // Add the number to its reverse for the next iteration
    }
    return lychrel; // Return the Lychrel property
}

// Function to reverse a number
unsigned long long int reverse(unsigned long long int i) {
    unsigned long long int ret = 0; // Declare and initialize variable to store reversed number
    while (i != 0) { // While loop to reverse the number
        ret *= 10; // Multiply ret by 10
        ret += i % 10; // Add the last digit of i to ret
        i /= 10; // Remove the last digit of i
    }
    return ret; // Return the reversed number
}

// Function to check if a number is a palindrome
bool palindrome(unsigned long long int i) {
    return (i == reverse(i)); // Return true if i is equal to its reverse, otherwise return false
}

Sample Output:

 Input a number: 196                                                                                          
 The given number is Lychrel.

Visual Presentation:

Flowchart:

C Programming Code Editor:

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