Add problem 72 - Edit Distance

Author: anirudhology

Diff for: problems/dynamic_programming/edit_distance.py

@@ -0,0 +1,21 @@
+class EditDistance:
+    @staticmethod
+    def minDistance(word1: str, word2: str) -> int:
+        # Lengths of the strings
+        m, n = len(word1), len(word2)
+        # Lookup table to store minimum operations required
+        lookup = [[0 for _ in range(n + 1)] for _ in range(m + 1)]
+        # Base initialization
+        for i in range(m + 1):
+            lookup[i][0] = i
+        for j in range(n + 1):
+            lookup[0][j] = j
+        # Populate the remaining table
+        for i in range(1, m + 1):
+            for j in range(1, n + 1):
+                # If current characters are same, we don't have to
+                # do anything
+                cost = 0 if word1[i - 1] == word2[j - 1] else 1
+                lookup[i][j] = min(cost + lookup[i - 1][j - 1], 1 + lookup[i - 1][j], 1 + lookup[i][j - 1])
+
+        return lookup[m][n]

Diff for: tests/dynamic_programming/edit_distance_test.py

@@ -0,0 +1,28 @@
+import unittest
+
+from problems.dynamic_programming.edit_distance import EditDistance
+
+
+class TestEditDistance(unittest.TestCase):
+
+    def setUp(self):
+        self.edit_distance = EditDistance()
+
+    def test_min_distance_empty_strings(self):
+        self.assertEqual(self.edit_distance.minDistance("", ""), 0)
+
+    def test_min_distance_one_empty_string(self):
+        self.assertEqual(self.edit_distance.minDistance("hello", ""), 5)
+        self.assertEqual(self.edit_distance.minDistance("", "java"), 4)
+
+    def test_min_distance_same_strings(self):
+        self.assertEqual(self.edit_distance.minDistance("same", "same"), 0)
+
+    def test_min_distance_different_strings(self):
+        self.assertEqual(self.edit_distance.minDistance("horse", "ros"), 3)
+        self.assertEqual(self.edit_distance.minDistance("intention", "execution"), 5)
+        self.assertEqual(self.edit_distance.minDistance("flaw", "lawn"), 2)
+
+
+if __name__ == "__main__":
+    unittest.main()