leeDistanceOf function

int leeDistanceOf(String source, String target, { int q = 1 << 16, KeyOf<String, int>? keyOf, bool ignoreCase = false, bool ignoreWhitespace = false, bool ignoreNumbers = false, bool alphaNumericOnly = false, })

Finds the Lee distance between two strings.

Parameters

• source and target are two strings.
• q is the alphabet size. It must be greater than 1. Default is 2^16
• If keyOf is present, it is used to get integer value of a character, otherwise the code unit value is used.
• if ignoreCase is true, the character case shall be ignored.
• if ignoreWhitespace is true, space, tab, newlines etc whitespace characters will be ignored.
• if ignoreNumbers is true, numbers will be ignored.
• if alphaNumericOnly is true, only letters and digits will be matched.

TIPS: You can pass both ignoreNumbers and alphaNumericOnly to true to ignore everything else except letters.

Details

In coding theory, Lee distance is a distance between two equal-length list of items over a q-ary alphabet {0, 1, ..., q - 1} of size q >= 2.

• The lee distance between two item x and y is min(|x - y|, q - |x - y|)
• The lee distance between two strings is the summation of all lee distances from index 0 to n.

If two list are not equal, a RangeError is thrown.

---

Complexity: Time O(n) | Space O(1)

Implementation

int leeDistanceOf(
  String source,
  String target, {
  int q = 1 << 16,
  KeyOf<String, int>? keyOf,
  bool ignoreCase = false,
  bool ignoreWhitespace = false,
  bool ignoreNumbers = false,
  bool alphaNumericOnly = false,
}) {
  source = cleanupString(
    source,
    ignoreCase: ignoreCase,
    ignoreWhitespace: ignoreWhitespace,
    ignoreNumbers: ignoreNumbers,
    alphaNumericOnly: alphaNumericOnly,
  );
  target = cleanupString(
    target,
    ignoreCase: ignoreCase,
    ignoreWhitespace: ignoreWhitespace,
    ignoreNumbers: ignoreNumbers,
    alphaNumericOnly: alphaNumericOnly,
  );

  List<int> s, t;
  if (keyOf == null) {
    s = source.codeUnits;
    t = target.codeUnits;
  } else {
    s = _extractKeys(source, keyOf);
    t = _extractKeys(target, keyOf);
  }

  return leeDistance(s, t, q);
}