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C Exercises: Find the largest palindrome made from the product of two 3-digit numbers

C Programming Practice: Exercise-20 with Solution

A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as taco cat or madam or racecar or the number 10801. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Write a C programming to find the largest palindrome made from the product of two 3-digit numbers.

C Code:

#include <stdio.h>
static int test_palindromic(unsigned int n);
int main(void)
{
  unsigned int i, j, max = 0;
  for (i = 100; i <= 999; i++) {
    for (j = 100; j <= 999; j++) {
      unsigned int p = i*j;
      if (test_palindromic(p) && p > max) {
        max = p;
      }
    }
  }
  printf("%u\n", max);
  return 0;
}
int test_palindromic(unsigned int n)
{
  unsigned int reversed_num = 0, t = n;
  while (t) {
    reversed_num = 10*reversed_num + (t % 10);
    t /= 10;
  }
  return reversed_num == n;
}

Sample Output:

906609

Flowchart:

C Programming Flowchart: Find the largest palindrome made from the product of two 3-digit numbers.

C Programming Code Editor:

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C Programming: Tips of the Day

The tilde operator in C:

The ~ operator is bitwise NOT, it inverts the bits in a binary number:

NOT 011100
  = 100011

Ref : https://bit.ly/3DR1N24