# 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;
}

## Output

If run the above code it will generate the following output −

109459