01-algorithmic_toolbox/04-dynamic_programming/03-edit_distance/edit_distance.cpp


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#include <iostream>
#include <string>

using std::string;

int edit_distance(const string &str1, const string &str2)
{
    int s1 = str1.length() + 1;
    int s2 = str2.length() + 1;
    int *m = new int[s1 * s2];

    for (int i = 0; i < s1; i++) m[i] = i;
    for (int i = 0; i < s2; i++) m[i * s1] = i;

    for (int i = 1; i < s2; i++) {
        for (int j = 1; j < s1; j++) {
            int insertion = m[i * s1 + j - 1] + 1;
            int deletion = m[(i - 1 ) * s1 + j] + 1;
            int match = m[(i - 1) * s1 + j - 1];
            int mismatch = match + 1;
            if (str2[i - 1] == str1[j - 1]) {
                /* m[i, j] = ((insertion < deletion) ? */
                m[i * s1 + j] = ((insertion < deletion) ?
                        ((insertion < match) ? insertion : match)
                        : ((deletion < match) ? deletion : match));
            }
            else {
                m[i * s1 + j] = ((insertion < deletion) ?
                        ((insertion < mismatch) ? insertion : mismatch)
                        : ((deletion < mismatch) ? deletion : mismatch));
            }
        }
    }

    /* for (int i = 0; i < s2; i++) { */
    /*     for (int j = 0; j < s1; j++) */
    /*         std::cout << m[i * s1 + j] << " "; */
    /*     std::cout << std::endl; */
    /* } */

    delete [] m;

    return m[s1 * s2 - 1];
}

int main() {
  string str1;
  string str2;
  std::cin >> str1 >> str2;
  std::cout << edit_distance(str1, str2) << std::endl;
  return 0;
}