Product of N with its largest odd digit in C

Given a number N with we have to product the number with its largest odd digit. If there is no odd digit then print -1.

Like we have initialized N with “153” and the largest odd digit in this number is 5 so the result would be the product of 153 with 5 i.e. 153 * 5 = 765 and if the number has no odd digit like 246 then the output must be -1.

Input − N = 198

Output − 1782

Explanation − 198 * 9 = 1782

Input − N = 15382

Output − 76910

Explanation − 15382 * 5 = 76910

Approach used below is as follows to solve the problem −

Take the input N.
Traverse every digit and look for odd digits
Find the largest odd element.
Product the largest off element with the original number N.
If there is no odd element update result with -1.
Return the result.

Algorithm

Start
In function int largestodd(int n)
   Step 1→ Declare and Initialize large as -1
   Step 2→ Loop While n > 0
      Set digit as n % 10
      If digit % 2 == 1 && digit > large then,
         Set large as digit
      Set n as n / 10
   Step 3→ Return large
In function int findproduct(int n)
   Step 1→ Declare and Initialize large set largestodd(n)
   Step 2→ If large == -1 then,
      Return -1
   Step 3→ Return (n * large)
In function int main()
   Step 1→ Initialize n as 15637
   Print the results from calling findproduct(n)
Stop

Example

Live Demo

#include <stdio.h>
int largestodd(int n){
   // If all digits are even then
   // we wil return -1
   int large = -1;
   while (n > 0) {
      // checking from the last digit
      int digit = n % 10;
      // If the current digit is odd and
      // is greater than the large
      if (digit % 2 == 1 && digit > large)
         large = digit;
      n = n / 10;
   }
   // To return the maximum
   // odd digit of n
   return large;
}
int findproduct(int n){
   int large = largestodd(n);
   // If there are no odd digits in n
   if (large == -1)
      return -1;
   // Product of n with its largest odd digit
   return (n * large);
}
int main(){
   int n = 15637;
   printf("%d
", findproduct(n));
   return 0;
}