Adding solution for Group Anagrams problem

README.md

@@ -21,6 +21,7 @@ Read documentation of this project [here](docs/index.md).
 * [Stacks and Queues](#stacks-and-queues)
 * [Trees and Graphs](#trees-and-graphs)
 * [Recursion and Dynamic Programming](#recursion-and-dynamic-programming)
+* [Sorting and Searching](#sorting_and_searching)
 
 
 ### Arrays and Strings
@@ -51,7 +52,14 @@ Read documentation of this project [here](docs/index.md).
 
 | Number | Problem                  | Solution                                                                                 |
 |:------:|:------------------------:|:----------------------------------------------------------------------------------------:|
-| 8.3    | Magic Index              | [Distinct elements][8_3_distinct], [Non distinct elements][8_3_non_distinct]    |
+| 8.3    | Magic Index              | [Distinct elements][8_3_distinct], [Non distinct elements][8_3_non_distinct]             |
+
+### Sorting and Searching
+
+| Number | Problem                  | Solution                                                                                 |
+|:------:|:------------------------:|:----------------------------------------------------------------------------------------:|
+| 10.2   | Group Anagrams           | [Brute Force][10_2_brute_force], [Improved][10_2_improved]                               |
+
 
 
 [cracking_the_coding_interview]: https://www.amazon.com/Cracking-Coding-Interview-Programming-Questions/dp/0984782850
@@ -65,3 +73,5 @@ Read documentation of this project [here](docs/index.md).
 [4_1_dfs]: solutions/trees_and_graphs/route_between_nodes.py#L12
 [8_3_distinct]: solutions/recursion_and_dynamic_programming/magic_index.py#L16
 [8_3_non_distinct]: solutions/recursion_and_dynamic_programming/magic_index.py#L40
+[10_2_brute_force]: solutions/sorting_and_searching/group_anagrams.py#L11
+[10_2_improved]: solutions/sorting_and_searching/group_anagrams.py#L47

solutions/sorting_and_searching/group_anagrams.py

@@ -0,0 +1,64 @@
+"""
+Problem
+
+    Write a method to sort an array of strings so that all the anagrams are
+    next to each other.
+"""
+from collections import defaultdict
+from typing import List, Dict
+
+
+class BruteForce:
+    """Brute force implementation of group anagrams"""
+
+    def _is_anagrams(self, string_1: str, string_2: str) -> bool:
+        if len(string_1) != len(string_2):
+            return False
+        character_count: Dict = defaultdict(int)
+        for character in string_1:
+            character_count[character] += 1
+        for character in string_2:
+            if (
+                (character not in character_count) or
+                (character_count[character] == 0)
+            ):
+                return False
+            else:
+                character_count[character] -= 1
+        return True
+
+    def sort(self, anagrams: List[str]) -> None:
+        if not anagrams:
+            return None
+        index = 0
+        while index < len(anagrams):
+            for index_of_left in range(index + 1, len(anagrams)):
+                if self._is_anagrams(
+                    anagrams[index], anagrams[index_of_left]
+                ):
+                    anagrams[index + 1], anagrams[index_of_left] = (
+                        anagrams[index_of_left], anagrams[index + 1]
+                    )
+                    break
+            index += 2
+        return
+
+
+class Improved:
+    """Improved implementation to group anagrams"""
+
+    def _calculate_score(self, anagram: str) -> int:
+        score = 0
+        for character in anagram:
+            score += ord(character)
+        return score
+
+    def sort(self, anagrams):
+        anagrams_collection = defaultdict(list)
+        while len(anagrams) != 0:
+            anagram = anagrams.pop()
+            score = self._calculate_score(anagram)
+            anagrams_collection[score].append(anagram)
+        for _, similar_anagrams in anagrams_collection.items():
+            for anagram in similar_anagrams:
+                anagrams.append(anagram)

solutions/sorting_and_searching/tests/test_group_anagrams.py

@@ -0,0 +1,40 @@
+from typing import Tuple
+
+from .. import group_anagrams
+
+
+def test_brute_force_sort():
+    sample_inputs_and_expected_outputs: Tuple = (
+        (
+            ["aa", "bb", "acca", "bb", "aa", "ccaa"],
+            ['aa', 'aa', 'acca', 'ccaa', 'bb', 'bb']
+        ),
+        ([], []),
+        (
+            ["a", "b", "c", "a", "b", "c"],
+            ["a", "a", "c", "c", "b", "b"]
+        )
+    )
+
+    brute_force = group_anagrams.BruteForce()
+    for anagrams, expected_anagrams in sample_inputs_and_expected_outputs:
+        brute_force.sort(anagrams)
+        assert anagrams == expected_anagrams
+
+
+def test_improved_sort():
+    sample_inputs_and_expected_outputs: Tuple = (
+        (
+            ["aa", "bb", "acca", "bb", "aa", "ccaa"],
+            ['ccaa', 'acca', 'aa', 'aa', 'bb', 'bb']
+        ),
+        ([], []),
+        (
+            ["a", "b", "c", "a", "b", "c"],
+            ['c', 'c', 'b', 'b', 'a', 'a']
+        )
+    )
+    improved = group_anagrams.Improved()
+    for anagrams, expected_anagrams in sample_inputs_and_expected_outputs:
+        improved.sort(anagrams)
+        assert anagrams == expected_anagrams