C program takes an absurdly long amount of time (or enters infinite loop)

Question

The function is given a string (for example "communism") and checks whether or not its suffix is a part of a wordbank - the program takes an absurdly long time (or is infinite-looped, I don't know but I suspect the first). here's an example of the suffix wordbank (reversed) char* noun_suffixes[] = { "msi", "re", "sci", "ssen", "tnem", "tsi" }; Here's the function: (n is the number of words in the bank, *str is the word).

bool is_suffix_in_dict(char* str, char* dict[], int n)
{
    printf("first checkpoint reached");
    char strRev[MAX_LEN + 1] = { 0 }, strToCheck[MAX_LEN + 1] = { 0 };
    unsigned int len = strlen(str);
    for (unsigned int i = 0; i < len; i++)
    {
        strRev[len - i] = *(str + i);
    }
    for (unsigned int i = 0, j = 0; i < len; i++)
    {
        while (strRev[i] < 'a' || strRev[i] > 'z')
        {
            i++;
        }
        if (i < len)
        {
            strToCheck[j] = strRev[i];
            if (binarySearch(dict, n, strToCheck))
            {
                printf("second check reached - positive");
                return TRUE;
            }
            j++;
        }
    }
    printf("second check reached - neg");
    return FALSE;
}

the function calls upon this one-

bool binarySearch(char* dict[], int n, char s[MAX_LEN + 1])
{
    int last = n, first = 0, mid = n / 2;
    while (first < n)
    {
        int cmpVal = strcmp(dict[mid], s);
        if (cmpVal < 0)
        {
            printf("cmpVal<0");
            first = mid + 1;
            mid = (first + last) / 2;
        }
        else if (cmpVal > 0)
        {
            printf("cmpVal>0");
            last = mid;
            mid = (first + last) / 2;
        }
        else
        {
            return TRUE;
        }
    }
    return FALSE;
}