What is the program for palindrome numbers from 500 to 100?

Answer 1

#include<iostream>

// forward declarations...

unsigned reverse (unsigned, const unsigned base = 10);

bool is_palindrome (const unsigned);

// the program...

int main (void) {

const unsigned max {500};

const unsigned min {100};

std::cout << "Palindromes from " << max << " to " << min << std::endl;

for (unsigned num {max}; num>=min; --num) {

if (is_palindrome (num)) {

std::cout << num << std::endl;

}

}

}

// Returns the reverse of a number using the given base (default: base 10)

// Note: trailing zeroes do not become leading zeroes so reverse (100) returns 1 not 001.

// However, the reverse of 0 is obviously 0.

unsigned reverse (unsigned num, const unsigned base /* = 10 */) {

unsigned rev {}; // zero-initialised

while (num) {

rev *= base;

rev += num % base;

num /= base;

}

return rev;

}

// If the reverse of a number is the same number, that number is a palindrome.

// All single-digit numbers are palindromes, including 0.

bool is_palindrome (const unsigned num) {

return num == reverse (num) ;

}