Interface/MueLu_ParameterListInterpreter.cpp

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//        MueLu: A package for multigrid based preconditioning
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#include <cstring>
#include <string>
#include <vector>
#include <algorithm>

namespace MueLu {

  size_t LevenshteinDistance(const char* s, size_t len_s, const char* t, size_t len_t) {
    // degenerate cases
    if (len_s == 0)                             return len_t;
    if (len_t == 0)                             return len_s;
    if (!strncmp(s, t, std::min(len_s, len_t))) return 0;

    // create two work vectors of integer distances
    size_t len = len_t + 1;
    std::vector<size_t> v0(len);
    std::vector<size_t> v1(len);

    // initialize v0 (the previous row of distances)
    // this row is A[0][i]: edit distance for an empty s
    // the distance is just the number of characters to delete from t
    for (size_t i = 0; i < len; i++)
      v0[i] = i;

    for (size_t i = 0; i < len_s; i++) {
      // calculate v1 (current row distances) from the previous row v0

      // first element of v1 is A[i+1][0]
      //   edit distance is delete (i+1) chars from s to match empty t
      v1[0] = i + 1;

      // use formula to fill in the rest of the row
      for (size_t j = 0; j < len_t; j++) {
        size_t cost = (s[i] == t[j]) ? 0 : 1;
        v1[j+1] = std::min(v1[j] + 1,
                  std::min(v0[j + 1] + 1,
                           v0[j] + cost));
      }

      // copy v1 (current row) to v0 (previous row) for next iteration
      for (size_t j = 0; j < len; j++)
        v0[j] = v1[j];
    }

    return v1[len_t];
  }

}