# PetroProtsyk/Sources

Switch branches/tags
Nothing to show
Fetching contributors…
Cannot retrieve contributors at this time
209 lines (184 sloc) 4.87 KB
 using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace SEA2016.FuzzySearch { /// /// Calculate Levenshtein distance between two strings using Dynamic Programming approach /// public static class LevenshteinDynamicProgramming { /// /// Wagner–Fischer algorithm with full matrix /// Time complexity: O(|a|*|b|) /// Memory complexity: O(|a|*|b|) /// https://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm /// public static int Calculate(string a, string b) { return CreateMatrix(a, b)[a.Length, b.Length]; } /// /// Wagner–Fischer algorithm that uses memory for two rows /// Time complexity: O(|a|*|b|) /// Memory complexity: O(max(|a|,|b|)) /// https://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm /// public static int CalculateMemoryOptimized(string a, string b) { if (a.Length < b.Length) { var t = a; a = b; b = t; } var d = new int[b.Length + 1]; var c = new int[b.Length + 1]; // Initialization for (int i = 0; i <= b.Length; i++) d[i] = i; // Calculation for (int i = 0; i < a.Length; i++) { c[0] = i + 1; for (int j = 0; j < b.Length; j++) { if (a[i] == b[j]) { c[j + 1] = d[j]; } else { c[j + 1] = 1 + Math.Min(d[j], Math.Min(d[j + 1], c[j])); } } var t = c; c = d; d = t; } return d[b.Length]; } /// /// Print steps to transform a to b /// public static TraceLog Trace(string a, string b) { return new TraceLog(a, b, CreateMatrix(a, b)); } private static int[,] CreateMatrix(string a, string b) { var d = new int[a.Length + 1, b.Length + 1]; // Initialization for (int i = 0; i <= a.Length; i++) d[i, 0] = i; for (int i = 0; i <= b.Length; i++) d[0, i] = i; // Calculation for (int i = 0; i < a.Length; i++) { for (int j = 0; j < b.Length; j++) { if (a[i] == b[j]) { d[i + 1, j + 1] = d[i, j]; } else { d[i + 1, j + 1] = 1 + Math.Min(d[i, j], Math.Min(d[i, j + 1], d[i + 1, j])); } } } return d; } public class TraceLog { private readonly int[,] d; private readonly string a; private readonly string b; internal TraceLog(string a, string b, int[,] d) { this.a = a; this.b = b; this.d = d; } public void PrintMatrix() { for (int i = 0; i <= a.Length; i++) { for (int j = 0; j <= b.Length; j++) { Console.Write(d[i, j] + " "); } Console.WriteLine(); } } public void PrintTransformations() { // Trace back int k = a.Length; int m = b.Length; int p = b.Length; var path = new Stack(); while ((k != 0) || (m != 0)) { int c = d[k, m]; if ((k > 0) && (m > 0) && (d[k - 1, m - 1] < c)) { k = k - 1; m = m - 1; --p; // \$"Sub {a[k]} with {b[m]} at position {p}" path.Push(new Action(1, p, b[m])); } else if ((k > 0) && (d[k - 1, m] < c)) { k = k - 1; path.Push(new Action(2, p, '\0')); // \$"Del {a[k]} at position {p}" } else if ((m > 0) && (d[k, m - 1] < c)) { m = m - 1; --p; // \$"Ins {b[m]} at position {p}" path.Push(new Action(3, p, b[m])); } else if ((k > 0) && (m > 0) && (d[k - 1, m - 1] == c)) { k = k - 1; m = m - 1; --p; } else if ((k > 0) && (d[k - 1, m] == c)) { k = k - 1; } else if ((m > 0) && (d[k, m - 1] == c)) { m = m - 1; } } var tr = new List(a); int counter = 0; Console.WriteLine(string.Format("{0}: {1}", counter, a)); while (path.Count > 0) { var action = path.Pop(); switch (action.type) { case 1: tr[action.position] = action.c; break; case 2: tr.RemoveAt(action.position); break; case 3: tr.Insert(action.position, action.c); break; } ++counter; Console.Write(string.Format("{0}: ", counter)); Console.WriteLine(new string(tr.ToArray())); } } } private struct Action { public readonly int type; public readonly int position; public readonly char c; public Action(int type, int position, char c) { this.type = type; this.position = position; this.c = c; } } } public static class Program { public static void Main(string[] args) { var words = Console.ReadLine().Split(' '); Console.WriteLine(\$"Distance between words {words[0]} and {words[1]} using dynamic programming algorithm:"); Console.WriteLine(LevenshteinDynamicProgramming.Calculate(words[0], words[1])); Console.WriteLine("Transformations:"); var trace = LevenshteinDynamicProgramming.Trace(words[0], words[1]); trace.PrintTransformations(); } } }