Find strings with lowest Hamming distance

Question

I have a list of (alphabetical) strings, and I want to compare a string against a list of other strings, and find which string has the lowest Hamming distance compared to that string. Also, the list of strings used for comparison is known at compile time.
I thought of something like this:

char* compare[10][10]; // Assume this array is filled with random strings, every string of length n is in row n - 1. 
int hamming_distance(char* x, char* y, int len); // I don't know of any fast ways to compute the Hamming distance between two alphabetical strings
int hamming_distance(char* x, char* y, int len) {
    int hamming_distance = 0;
    for(i = 0; i <= len; i++) {
        if(x[i] != y[i]) {
            hamming_distance++;
        }
    }
    return hamming_distance;
}
char* lowest_hamming_distance(char* x);
char* lowest_hamming_distance(char* x) {
    int minhammingdistance = INT_MAX;
    int currenthammingdistance;
    int len = strlen(x) - 1;
    for( i = 0; i < 10; i++) {
        currenthammingdistance = hamming_distance(compare[len][i], x, len);
        if(minhammingdistance > currenthammingdistance) {
            minhammingdistance = currenthammingdistance;
            int min_hamming_distance_string = i;
        }
    }
    return compare[len][min_hanmming_distance_string];
}

Add the [tag:algorithm] tag if you want a concept. What is wrong with your current algorithm? (If so.) — Jongware, May 01 '16 at 11:22
@RadLexus I'm asking whether there's a fast way to find the Hamming distance between two strings, and if there's a faster way to do the comparison, other than my current algorithm. — Mitsos101, May 01 '16 at 11:29
Compare string lengths, if different return `-1`. Let `total = 0` Iterate over each `char` in both _Strings_ (at the same time), if left char does not equal right char, `total += 1`. Return `total` — Paul S., May 01 '16 at 11:32
@Mitsos101, please put the question you gave in comments, in your ... question. Because there you are not asking anything. NB: The algorithm you have for `hamming_distance` after your latest edit, is *O(n)*, which cannot be improved (as you need to verify each character anyway). — trincot, May 01 '16 at 11:38
`for(i = 0; i <= len; i++) {` this accesses the string beyond its size. — wildplasser, May 01 '16 at 11:40
@wildplasser How so? The len parameter passed to the function is equal to the length - 1. — Mitsos101, May 01 '16 at 12:27

Find strings with lowest Hamming distance

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