ones.c

#include <stdio.h>
#include <stdlib.h>

static int prime_factor(int n, int *factors, int *factors_size);
static void expand_arr(int **arr, int *size);
static void make_into_ones(int x);

int main(void) {

    int n; scanf("%d", &n);

    int *factors = NULL;
    int factors_size = 0;
    expand_arr(&factors, &factors_size);

    int cnt = prime_factor(n, factors, &factors_size);

    for (int i = 0; i < cnt; i++) {
        make_into_ones(factors[i]);
        if (i != cnt - 1) printf("*");
    }
    printf("\n");

    free(factors);

    return 0;
}

static int prime_factor(int n, int *factors, int *factors_size) {
    if (n < 0) n *= -1;

    int x = 2, cnt = 0;
    while (n > 1) {
        if (n % x == 0) {
            n /= x;
            if (cnt >= *factors_size) {
                expand_arr(&factors, factors_size);
            }
            factors[cnt++] = x;
            x = 2;
        } else {
            x++;
        }
    }
    return cnt;
}

static void expand_arr(int **arr, int *size) {
    int *tmp = realloc( *arr, sizeof(int) * (2 * (*size) + 1));
    if (tmp == NULL) {
        fprintf(stderr, "Ran outta memory!");
        exit(1);
    }
    *arr = tmp;
    *size = 2 * (*size) + 1;
}

static void make_into_ones(int x) {
    if (x < 1) return;
    printf("(");
    for (int i = 1; i < x; i++) {
        printf("1+");
    }
    printf("1)");
}