Add Edit Distance algorithm with tests

dp/edit_distance.py

@@ -0,0 +1,37 @@
+def edit_distance(str1, str2):
+    """
+    Calculate the minimum number of operations required to convert str1 into str2.
+    Operations allowed: insertion, deletion, substitution.
+    
+    :param str1: First string
+    :param str2: Second string
+    :return: Minimum number of operations required
+    """
+    m, n = len(str1), len(str2)
+
+    # Create a matrix to store the subproblem solutions
+    dp = [[0] * (n + 1) for _ in range(m + 1)]
+
+    # Initialize the first row and column
+    for i in range(m + 1):
+        dp[i][0] = i
+    for j in range(n + 1):
+        dp[0][j] = j
+
+    # Fill the dp matrix
+    for i in range(1, m + 1):
+        for j in range(1, n + 1):
+            if str1[i-1] == str2[j-1]:
+                dp[i][j] = dp[i-1][j-1]
+            else:
+                dp[i][j] = 1 + min(dp[i-1][j],      # deletion
+                                   dp[i][j-1],      # insertion
+                                   dp[i-1][j-1])    # substitution
+
+    return dp[m][n]
+
+# Example usage
+if __name__ == "__main__":
+    str1 = "kitten"
+    str2 = "sitting"
+    print(f"Edit distance between '{str1}' and '{str2}': {edit_distance(str1, str2)}")

dp/test_edit_distance.py

@@ -0,0 +1,26 @@
+import unittest
+from edit_distance import edit_distance
+
+class TestEditDistance(unittest.TestCase):
+    def test_basic_cases(self):
+        self.assertEqual(edit_distance("kitten", "sitting"), 3)
+        self.assertEqual(edit_distance("horse", "ros"), 3)
+        self.assertEqual(edit_distance("intention", "execution"), 5)
+
+    def test_edge_cases(self):
+        self.assertEqual(edit_distance("", ""), 0)
+        self.assertEqual(edit_distance("", "abc"), 3)
+        self.assertEqual(edit_distance("abc", ""), 3)
+        self.assertEqual(edit_distance("abc", "abc"), 0)
+
+    def test_single_character_operations(self):
+        self.assertEqual(edit_distance("a", "b"), 1)  # substitution
+        self.assertEqual(edit_distance("a", "ab"), 1)  # insertion
+        self.assertEqual(edit_distance("ab", "a"), 1)  # deletion
+
+    def test_long_strings(self):
+        self.assertEqual(edit_distance("pneumonoultramicroscopicsilicovolcanoconiosis",
+                                       "ultramicroscopically"), 27)
+
+if __name__ == '__main__':
+    unittest.main()