feat: solve 49. Group Anagrams with unit testing

README.md

@@ -15,8 +15,8 @@
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@@ -184,6 +184,7 @@ This repository covers a comprehensive range of algorithmic patterns and data st
 | # | Title | Solution | Time | Space | Difficulty | Tag | Note |
 |---|-------|----------|------|-------|------------|-----|------|
 | 1 | [Two Sum](https://leetcode.com/problems/two-sum/) | [Python](./problems/two_sum/two_sum.py), [C++](./problems/two_sum/two_sum.cc) | _O(n)_ | _O(n)_ | Easy |  |  |
+| 49 | [Group Anagrams](https://leetcode.com/problems/group-anagrams/) | [Python](./problems/group_anagrams/group_anagrams.py), [C++](./problems/group_anagrams/group_anagrams.cc) | _O(n * k log k)_ | _O(n)_ | Medium |  | For C++, the complexity is _O(n * k log k)_, where n is the number of strings and k is the maximum length of a string. But for Python, the complexity is _O(n * k)_ as there is no sorting involved. |
 | 217 | [Contains Duplicate](https://leetcode.com/problems/contains-duplicate/) | [Python](./problems/contains_duplicate/contains_duplicate.py), [C++](./problems/contains_duplicate/contains_duplicate.cc) | _O(n)_ | _O(n)_ | Easy |  |  |
 
 ## Two Pointers

problems/group_anagrams/config.yml

@@ -0,0 +1,17 @@
+problem:
+  number: 49
+  title: "Group Anagrams"
+  leetcode_url: "https://leetcode.com/problems/group-anagrams/"
+  difficulty: "medium"
+  tags: ["Arrays & Hashing"]
+
+solutions:
+  python: "problems/group_anagrams/group_anagrams.py"
+  cpp: "problems/group_anagrams/group_anagrams.cc"
+
+complexity:
+  time: "O(n * k log k)"
+  space: "O(n)"
+
+notes: "For C++, the complexity is _O(n * k log k)_, where n is the number of strings and k is the maximum length of a string. But for Python, the complexity is _O(n * k)_ as there is no sorting involved."
+readme_link: ""

problems/group_anagrams/group_anagrams.cc

@@ -0,0 +1,28 @@
+#include "group_anagrams.h"
+
+#include <algorithm>
+#include <ranges>  // NOLINT(misc-include-cleaner) needed for std::ranges::sort
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+using namespace std;
+
+vector<vector<string>> groupAnagrams(vector<string>& strs) {
+    unordered_map<string, vector<string>> groups;
+    groups.reserve(strs.size());
+
+    for (const string& s : strs) {
+        string key = s;
+        std::ranges::sort(key);  // anagrams share the same sorted key
+        groups[key].push_back(s);
+    }
+
+    vector<vector<string>> res;
+    res.reserve(groups.size());
+    for (auto& [k, v] : groups) {
+        res.push_back(std::move(v));
+    }
+    return res;
+}

problems/group_anagrams/group_anagrams.h

@@ -0,0 +1,4 @@
+#include <string>
+#include <vector>
+
+std::vector<std::vector<std::string>> groupAnagrams(std::vector<std::string>& strs);

problems/group_anagrams/group_anagrams.py

@@ -0,0 +1,13 @@
+import collections
+
+from typing import List
+
+
+def groupAnagrams(strs: List[str]) -> List[List[str]]:
+    groups = collections.defaultdict(list)
+    for s in strs:
+        count = [0] * 26
+        for c in s:
+            count[ord(c) - ord("a")] += 1
+        groups[tuple(count)].append(s)
+    return list(groups.values())

problems/group_anagrams/group_anagrams_test.cc

@@ -0,0 +1,65 @@
+#include "group_anagrams.h"
+
+#include <gtest/gtest.h>
+#include <algorithm>
+#include <ranges>  // NOLINT(misc-include-cleaner) needed for std::ranges::sort
+#include <string>
+#include <vector>
+
+struct GroupAnagramsCase {
+    std::string test_name;
+    std::vector<std::string> strs;
+    std::vector<std::vector<std::string>> expected;
+};
+
+using GroupAnagramsTest = ::testing::TestWithParam<GroupAnagramsCase>;
+
+namespace {
+// Helper function to sort and compare results
+bool compareResults(std::vector<std::vector<std::string>> result,
+                    std::vector<std::vector<std::string>> expected) {
+    // Sort inner vectors and outer vector for comparison
+    for (auto& group : result) {
+        std::ranges::sort(group);
+    }
+    std::ranges::sort(result);
+
+    for (auto& group : expected) {
+        std::ranges::sort(group);
+    }
+    std::ranges::sort(expected);
+
+    return result == expected;
+}
+}  // namespace
+
+TEST_P(GroupAnagramsTest, TestCases) {
+    const GroupAnagramsCase& testCase = GetParam();
+    std::vector<std::string> input = testCase.strs;  // Make a copy since function might modify
+    const std::vector<std::vector<std::string>> result = groupAnagrams(input);
+    EXPECT_TRUE(compareResults(result, testCase.expected));
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    GroupAnagramsTestCases, GroupAnagramsTest,
+    ::testing::Values(
+        GroupAnagramsCase{.test_name = "BasicCase",
+                          .strs = {"eat", "tea", "tan", "ate", "nat", "bat"},
+                          .expected = {{"bat"}, {"tan", "nat"}, {"eat", "tea", "ate"}}},
+        GroupAnagramsCase{.test_name = "SingleEmptyString", .strs = {""}, .expected = {{""}}},
+        GroupAnagramsCase{.test_name = "SingleCharacter", .strs = {"a"}, .expected = {{"a"}}},
+        GroupAnagramsCase{.test_name = "MultipleAnagramGroups",
+                          .strs = {"abc", "bca", "cab", "xyz", "zyx", "yxz"},
+                          .expected = {{"abc", "bca", "cab"}, {"xyz", "zyx", "yxz"}}},
+        GroupAnagramsCase{
+            .test_name = "LongerStrings",
+            .strs = {"listen", "silent", "enlist", "inlets", "google", "gogole"},
+            .expected = {{"listen", "silent", "enlist", "inlets"}, {"google", "gogole"}}},
+        GroupAnagramsCase{.test_name = "AllAnagrams",
+                          .strs = {"aabb", "abab", "bbaa", "baba", "abba"},
+                          .expected = {{"aabb", "abab", "bbaa", "baba", "abba"}}},
+        GroupAnagramsCase{.test_name = "MixedLengths",
+                          .strs = {"rat", "tar", "art", "star", "tars"},
+                          .expected = {{"rat", "tar", "art"}, {"star", "tars"}}},
+        GroupAnagramsCase{.test_name = "EmptyList", .strs = {}, .expected = {}}),
+    [](const ::testing::TestParamInfo<GroupAnagramsCase>& info) { return info.param.test_name; });

problems/group_anagrams/group_anagrams_test.py

@@ -0,0 +1,53 @@
+"""Test cases for the group_anagrams function."""
+
+import pytest
+
+from group_anagrams import groupAnagrams
+
+
+@pytest.mark.parametrize(
+    "strs, expected",
+    [
+        (
+            ["eat", "tea", "tan", "ate", "nat", "bat"],
+            [["bat"], ["tan", "nat"], ["eat", "tea", "ate"]],
+        ),  # Basic case
+        ([""], [[""]]),  # Single empty string
+        (["a"], [["a"]]),  # Single character
+        (
+            ["abc", "bca", "cab", "xyz", "zyx", "yxz"],
+            [["abc", "bca", "cab"], ["xyz", "zyx", "yxz"]],
+        ),  # Multiple anagram groups
+        (
+            ["listen", "silent", "enlist", "inlets", "google", "gogole"],
+            [["listen", "silent", "enlist", "inlets"], ["google", "gogole"]],
+        ),  # Longer strings
+        (
+            ["aabb", "abab", "bbaa", "baba", "abba"],
+            [["aabb", "abab", "bbaa", "baba", "abba"]],
+        ),  # All are anagrams
+        (
+            ["rat", "tar", "art", "star", "tars"],
+            [["rat", "tar", "art"], ["star", "tars"]],
+        ),  # Mixed lengths
+        ([], []),  # Empty list
+    ],
+    ids=[
+        "basic_case",
+        "single_empty_string",
+        "single_character",
+        "multiple_anagram_groups",
+        "longer_strings",
+        "all_anagrams",
+        "mixed_lengths",
+        "empty_list",
+    ],
+)
+def test_group_anagrams(strs, expected):
+    result = groupAnagrams(strs)
+    # Sort inner lists and the outer list for comparison
+    result = [sorted(group) for group in result]
+    result.sort()
+    expected = [sorted(group) for group in expected]
+    expected.sort()
+    assert result == expected