Clash Royale CLAN TAG

Writing a string repeater in C produces unwanted chars

I'm trying to get a custom string repeater to work in C. It works for some input, and in other cases it appends unwanted characters. It seem to me malloc in some cases allocates too much memory, but I don't quite grasp why.

malloc

Examples:

repeater("hi", 2) -> hihi

repeater("hi", 2) -> hihi

repeater("yeah", 4) -> yeahyeahyeahyeah?f{??

repeater("yeah", 4) -> yeahyeahyeahyeah?f{??

The code:

int length(char* str)
{
int i;
if(str == NULL)
return 0;
for(i = 0; *(str+i) != ''; ++i);
return i;
}

char* repeater(char* str, int times)
{
char* out;
int i,len,sz;
len = length(str);
sz = len * times;
out = (char*)malloc(sz * sizeof(char));
for(i = 0; i < sz; i++)
*(out+i) = *(str + (i % len));
return out;
}


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