Most common substring of length X

Question

I have a string s and I want to search for the substring of length X that occurs most often in s. Overlapping substrings are allowed.

For example, if s=\"aoaoa\" and X=3

Answer 1

Here is a version I did in C. Hope that it helps.

#include 
#include 
#include 

int main(void)
{
    char *string = NULL, *maxstring = NULL, *tmpstr = NULL, *tmpstr2 = NULL;
    unsigned int n = 0, i = 0, j = 0, matchcount = 0, maxcount = 0;

    string = "aoaoa";
    n = 3;

    for (i = 0; i <= (strlen(string) - n); i++) {
        tmpstr = (char *)malloc(n + 1);
        strncpy(tmpstr, string + i, n);
        *(tmpstr + (n + 1)) = '\0';
        for (j = 0; j <= (strlen(string) - n); j++) {
            tmpstr2 = (char *)malloc(n + 1);
            strncpy(tmpstr2, string + j, n);
            *(tmpstr2 + (n + 1)) = '\0';
            if (!strcmp(tmpstr, tmpstr2))
                matchcount++;
        }
        if (matchcount > maxcount) {
            maxstring = tmpstr;
            maxcount = matchcount;
        }
        matchcount = 0;
    }

    printf("max string: \"%s\", count: %d\n", maxstring, maxcount);

    free(tmpstr);
    free(tmpstr2);

    return 0;
}