C Exercises: Find all prime palindromes in the range of two given numbers x and y

Last update on December 20 2024 13:14:53 (UTC/GMT +8 hours)

List all prime palindromes between two given numbers

Write a C program to find all prime palindromes in the range of two given numbers x and y (5 <= x<y<= 1000,000,000).
A number is called a prime palindrome if the number is both a prime number and a palindrome.

Sample Solution:

C Code:

#include<stdio.h>

// Function to compute a palindrome number from a given number
int compute(int n){
	if(n == 9) // Special case for n = 9
		return 11; // Return 11
	int res = 0, tmp, base = 1;

	// Loop to reverse the digits of n
	for(tmp = n / 10; tmp> 0; tmp = tmp / 10){
		res = res * 10 + tmp % 10; // Build the reversed number
		base *= 10;
	}

	return n * base + res; // Combine the original and reversed numbers
}

// Function to check if a number is prime and print it if it is
int prime(int n){
	int i;
	int flag;

	// Loop to check for factors of n
	for(i = 2; i * i<= n; i++){
		flag = 0;
		if(n % i == 0){
			flag = 1; // Set flag to indicate non-prime
			break;
		}
	}

	if(flag == 0){ // If flag remains 0, n is a prime number
		printf("%d\n", n); // Print the prime number
	}
}

int main(){
	int x, y, temp = 0;

	printf("Input two numbers (separated by a space):\n");
	scanf("%d %d", &x, &y);

	printf("List of prime palindromes:\n");

	// Loop to generate and check palindrome numbers
	for(; temp <= y; x++){
		temp = compute(x);
		prime(temp);
	}

	return 0; // Indicate successful execution of the program
}

Sample Output:

Input two numbers (separated by a space):
List of prime palindromes:
0
1

Flowchart:

C programming Code Editor:

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