用C乘以字符串

Question

I wrote a simple program to multiply a string a defined times. But, it doesn't really work, and don't know why...

It's so simple that I don't know what the problem could be...

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

char *product(char *str, int k);

int main()
{
    char strg[1000];
    char *prod;
    int mult;

    scanf("%s", strg);
    scanf("%d", mult);

    prod = product(strg, mult);

    printf("%s\n", prod);

    return EXIT_SUCCESS;
}

char *product(char *str, int k)
{
    int i, j;
    int len = strlen(str);
    char *res = (char *) malloc(sizeof(char) * (len * k + 1));

    for (i = 0, j = 0; i < (len * k); i++, j++)
    {
            if (j == len) j = 0;

            res[i] = str[j];
    }

    res[++i] = '\0';

    return res;
}

Anyone who can help me to figure out where's the problem? :D

Answer 1

At the end of the loop, i is already the index of the position for the terminator.

Just do

res[i] = 0;