From 6ce99e49c4392ed4a6ff692eb27005a0f69504e5 Mon Sep 17 00:00:00 2001
From: Yuri Filgueira <yurimedeiros141@gmail.com>
Date: Thu, 30 May 2024 14:36:58 -0300
Subject: [PATCH] Feat: Levenshtein distance algorithm

---
 .../strings/LevenshteinDistance.java          | 57 +++++++++++++++++++
 .../strings/LevenshteinDistanceTest.java      | 51 +++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 src/main/java/com/williamfiset/algorithms/strings/LevenshteinDistance.java
 create mode 100644 src/test/java/com/williamfiset/algorithms/strings/LevenshteinDistanceTest.java

diff --git a/src/main/java/com/williamfiset/algorithms/strings/LevenshteinDistance.java b/src/main/java/com/williamfiset/algorithms/strings/LevenshteinDistance.java
new file mode 100644
index 000000000..081c1613a
--- /dev/null
+++ b/src/main/java/com/williamfiset/algorithms/strings/LevenshteinDistance.java
@@ -0,0 +1,57 @@
+package com.williamfiset.algorithms.strings;
+
+public class LevenshteinDistance {
+
+  // The Levenshtein distance algorithm calculates the minimum number of edits
+  // (insertions, deletions, or substitutions) needed to transform one string
+  // into another. It utilizes a matrix to store the distances between all
+  // prefixes of the two strings, and iteratively fills this matrix using
+  // dynamic programming. The final value in the matrix represents the
+  // Levenshtein distance between the two original strings.
+  public int calculateDistance(String origin, String destiny) {
+    int rows = origin.length();
+    int columns = destiny.length();
+
+    if (rows == 0 && columns == 0) {
+      return 0;
+    } else if (rows == 0) {
+      return columns;
+    } else if (columns == 0) {
+      return rows;
+    }
+
+    int[][] distance = new int[rows + 1][columns + 1];
+
+    for (int i = 0; i <= rows; i++) {
+      distance[i][0] = i;
+    }
+
+    for (int i = 0; i <= columns; i++) {
+      distance[0][i] = i;
+    }
+
+    for (int i = 1; i <= rows; i++) {
+      for (int j = 1; j <= columns; j++) {
+        if (origin.charAt(i - 1) == destiny.charAt(j - 1)) {
+          distance[i][j] = distance[i - 1][j - 1];
+        } else {
+          distance[i][j] =
+              1
+                  + Math.min(
+                      distance[i][j - 1], Math.min(distance[i - 1][j], distance[i - 1][j - 1]));
+        }
+      }
+    }
+
+    return distance[rows][columns];
+  }
+
+  public static void main(String[] args) {
+    LevenshteinDistance levenshteinDistance = new LevenshteinDistance();
+
+    String origin = "Rust is a good language";
+    String destiny = "Java is a good language";
+
+    System.out.println(levenshteinDistance.calculateDistance(origin, destiny));
+  }
+}
diff --git a/src/test/java/com/williamfiset/algorithms/strings/LevenshteinDistanceTest.java b/src/test/java/com/williamfiset/algorithms/strings/LevenshteinDistanceTest.java
new file mode 100644
index 000000000..7b24fda96
--- /dev/null
+++ b/src/test/java/com/williamfiset/algorithms/strings/LevenshteinDistanceTest.java
@@ -0,0 +1,51 @@
+package com.williamfiset.algorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class LevenshteinDistanceTest {
+
+  private LevenshteinDistance levenshteinDistance;
+
+  @BeforeEach
+  public void setUp() {
+    levenshteinDistance = new LevenshteinDistance();
+  }
+
+  @Test
+  public void calculateDistanceTest() {
+    assertEquals(2, levenshteinDistance.calculateDistance("Java", "javac"));
+    assertEquals(1, levenshteinDistance.calculateDistance("Rust", "rust"));
+    assertEquals(0, levenshteinDistance.calculateDistance("Spring", "Spring"));
+    assertEquals(0, levenshteinDistance.calculateDistance("Rest API", "Rest API"));
+    assertEquals(3, levenshteinDistance.calculateDistance("Rest API", "Rest api"));
+    assertEquals(
+        416,
+        levenshteinDistance.calculateDistance(
+            "gPfjkLwbvCdRmnXiQhZtyuEsWvaYozLqBMneRxPqOmgLjdSkFzuVrCtXpoKmBvJnzTiSqWmxOtPqlReVdSkiUmW"
+                + "vtXyNpsJfZoElQuRhKjGnLbZtYuVmAsPnRjMiQxOeLsKmWpTvZcQdNfHbRvTyWlXpMjOoKbZvFnTrXsPnMdJlQyUwHrKjGmAzXoVoPqTiS"
+                + "fYzUcNdLgKjBvQrXySnJtZlMpFqWvGsNzIrYoXtPuKdVcQhWpYlRnMgJsKqOtPiYxZrCwFvShNtLkMoQjTxUbWrXpVzFmJrGuSnOpKzJyR"
+                + "mQhPzTlWvBqMvJkKsLnGrXyFtNkZoPqJmEyWsFuCzHrRkTuLbJoQvNfGtYwVrYsXzPqLeVjTdKcWoMnZbRfHuJpXqNsMiVvZoFtKlDjUyN"
+                + "rVwYtPsBoLgKvZdHrLqUmXpNzJwOvFyRdHtCsKxVmPoJzWbQvShLpNr",
+            "nWjPuQfRkTgLxMbVhZySdIcKnOwXoEqVzCjBpSlDrUmAtYvJzWgNxQmUoErCsPlRfTgLbVwXtMjQhXvNsMpKzDrYcVtWlBzJsPkQnUvHaZr"
+                + "LdNiVwQmGfXoUeArSkQmWtHpVrLyQkNwTrXsUzDcKoJmLvHpRkYoQwUsFiXbMjGtVkPnWoUsXvZfRqOiTnLrGmYqKsPhXwDbTjLgVkQpNj"
+                + "WxFbErVhMuCnXoWpVjLbZqTdWmHpZkUfQiSnJrXaZtKpLwGrOzWyLsUmQjNvGvFbXuLqPsNrMnXtViQkVpOySqMuKtPcNrRzLhJxWoVfQrX"
+                + "lGrQyKdXnJiMtPsBuLoGfWzTdVjIrCoZlHsXpNmVpKrOhRfXwGpWvBsKjOyTvDbMiVjTuYpQrKnYuLbPzFhUpQsMlJtWsNrVoPjXnKzRdIkNxSfOlRpKrUhPq"));
+  }
+
+  public @Test void calculateDistanceWithEmptyOriginTest() {
+    assertEquals(9, levenshteinDistance.calculateDistance("", "Algorithm"));
+  }
+
+  @Test
+  public void calculateDistanceWithEmptyDestinyTest() {
+    assertEquals(9, levenshteinDistance.calculateDistance("Algorithm", ""));
+  }
+
+  @Test
+  public void calculateDistanceWithTwoEmptyStringsTest() {
+    assertEquals(0, levenshteinDistance.calculateDistance("", ""));
+  }
+}