How to remove the first * of my output in a C program?

Question

i'm trying to write a program that print the prime factors of a given number, but i need to print them separeted by *, for example: for the input 100 the output will be: 2*2*5*5, any suggestions? i did this so far:

# include <stdio.h> 
# include <math.h> 

void decomposicao(int n) 
{ 
    printf("%d = ", n);

    while (n%2 == 0) 
    { 
        n = n/2;
        printf("* %d ", 2); 
    } 

    for (int i = 3; i <= sqrt(n); i = i+2) 
    { 
        while (n%i == 0) 
        { 
            n = n/i; 
            printf("* %d ", i);     
        } 
    } 

    if (n > 2) 
        printf ("* %d ", n); 

} 
int main() 
{ 
    int n;

    scanf("%d", &n);

    if (n<=0||n==1)     
    {   
        printf("Error", n);
    }
    else
    {
        decomposicao(n);
    }   

    return 0; 
}

For this code the output is :

100 = *2*2*5*5

Answer 1

Add a boolean variable that tells you whether you're printing the first factor or not.

#include <stdbool.h>

void decomposicao(int n) 
{ 
    bool first = true;
    printf("%d = ", n);

    while (n%2 == 0) 
    { 
        n = n/2;
        if (!first)
            printf("* ");

        printf("%d ", 2); 
        first = false;
    } 

    for (int i = 3; i <= sqrt(n); i = i+2) 
    { 
        while (n%i == 0) 
        { 
            n = n/i; 
            if (!first)
                printf("* ");

            printf("%d ", i);
            first = false;  
        } 
    } 

    if (n > 2) {
        if (!first)
            printf("* ");

        printf ("%d ", n); 
    }
}