# Edit distance function

Could you please help me to review my first function (modified from an example) in terms of best practice, coding style suggestions and any obvious language mistake/improvements?

unsigned int edit_distance(const vector<string> &s1, const vector<string> &s2)
{
const size_t len1 = s1.size(), len2 = s2.size();
vector<vector<unsigned int>> d(len1 + 1, vector<unsigned int>(len2 + 1));

d[0][0] = 0;
for(unsigned int i = 1; i <= len1; ++i) d[i][0] = i;
for(unsigned int i = 1; i <= len2; ++i) d[0][i] = i;

for(unsigned int i = 1; i <= len1; ++i)
for(unsigned int j = 1; j <= len2; ++j)
{
unsigned int a = d[i - 1][j] + 1;
unsigned int b = d[i][j - 1] + 1;
unsigned int c = d[i - 1][j - 1] + (s1[i - 1] == s2[j - 1] ? 0 : 1);
d[i][j] = std::min( std::min(a,b), c);
}
return d[len1][len2];
}

• For starters you need a function comment, explain what its doing, use readable variable names. You don't get any performance improvement from minified code. Jun 12 '13 at 13:59

Do you want unsigned int or do you want std::size_t?

unsigned int edit_distance(const vector<string> &s1, const vector<string> &s2)


It comes down to what you are trying to convey.
The use of string and vector suggests you are doing using namespace std; try not to do this. Prefer to qualify your types: std::string and std::vector.

Personally, I prefer const on the right. But it's only a preference thing.

Only declare one variable per line:

    const size_t len1 = s1.size(), len2 = s2.size();


Come up with better names. d is not very descriptive.

    vector<vector<unsigned int>> d(len1 + 1, vector<unsigned int>(len2 + 1));


I would prefer std::size_t here:

    for(unsigned int i = 1; i <= len1; ++i) d[i][0] = i;