Added Levenshtein distance (a.k.a edit distance) algorithm to strings directory

String/LevenshteinDistance.test.js

@@ -0,0 +1,26 @@
+import levenshteinDistance from './LevenshteinDistance'
+
+describe('levenshteinDistance', () => {
+  it('should calculate edit distance between two strings', () => {
+    expect(levenshteinDistance('', '')).toBe(0)
+    expect(levenshteinDistance('a', '')).toBe(1)
+    expect(levenshteinDistance('', 'a')).toBe(1)
+    expect(levenshteinDistance('abc', '')).toBe(3)
+    expect(levenshteinDistance('', 'abc')).toBe(3)
+
+    // Should just add I to the beginning.
+    expect(levenshteinDistance('igloo', 'gloo')).toBe(1)
+
+    // Should just substitute i with o, m with g and insert e at end
+    expect(levenshteinDistance('firm', 'forge')).toBe(3)
+
+    // Should just substitute i with s, g with i, h with t and delete f from front
+    expect(levenshteinDistance('fighting', 'sitting')).toBe(4)
+
+    // Should add 4 letters b, a, s and e at the beginning.
+    expect(levenshteinDistance('ball', 'baseball')).toBe(4)
+
+    // Should delete 4 letters b, a, s and e at the beginning.
+    expect(levenshteinDistance('baseball', 'foot')).toBe(4)
+  })
+})