feat: add Majority Element

Author: wislertt

.templates/leetcode/json/majority_element.json

@@ -0,0 +1,43 @@
+{
+    "problem_name": "majority_element",
+    "solution_class_name": "Solution",
+    "problem_number": "169",
+    "problem_title": "Majority Element",
+    "difficulty": "Easy",
+    "topics": "Array, Hash Table, Divide and Conquer, Sorting, Counting",
+    "tags": ["grind-75"],
+    "readme_description": "Given an array `nums` of size `n`, return the majority element.\n\nThe majority element is the element that appears more than `\u230an / 2\u230b` times. You may assume that the majority element always exists in the array.",
+    "readme_examples": [
+        { "content": "```\nInput: nums = [3,2,3]\nOutput: 3\n```" },
+        { "content": "```\nInput: nums = [2,2,1,1,1,2,2]\nOutput: 2\n```" }
+    ],
+    "readme_constraints": "- n == nums.length\n- 1 <= n <= 5 * 10^4\n- -10^9 <= nums[i] <= 10^9",
+    "readme_additional": "**Follow-up:** Could you solve the problem in linear time and in O(1) space?",
+    "solution_imports": "",
+    "solution_methods": [
+        {
+            "name": "majority_element",
+            "parameters": "nums: list[int]",
+            "return_type": "int",
+            "dummy_return": "0"
+        }
+    ],
+    "test_imports": "import pytest\nfrom leetcode_py.test_utils import logged_test\nfrom .solution import Solution",
+    "test_class_name": "MajorityElement",
+    "test_helper_methods": [
+        { "name": "setup_method", "parameters": "", "body": "self.solution = Solution()" }
+    ],
+    "test_methods": [
+        {
+            "name": "test_majority_element",
+            "parametrize": "nums, expected",
+            "parametrize_typed": "nums: list[int], expected: int",
+            "test_cases": "[([3,2,3], 3), ([2,2,1,1,1,2,2], 2), ([1], 1), ([1,1,2], 1), ([2,2,2,1,1], 2)]",
+            "body": "result = self.solution.majority_element(nums)\nassert result == expected"
+        }
+    ],
+    "playground_imports": "from solution import Solution",
+    "playground_test_case": "# Example test case\nnums = [3,2,3]\nexpected = 3",
+    "playground_execution": "result = Solution().majority_element(nums)\nresult",
+    "playground_assertion": "assert result == expected"
+}

Makefile

@@ -1,5 +1,5 @@
 PYTHON_VERSION = 3.13
-PROBLEM ?= climbing_stairs
+PROBLEM ?= majority_element
 FORCE ?= 0
 COMMA := ,
 

leetcode/majority_element/README.md

@@ -0,0 +1,37 @@
+# Majority Element
+
+**Difficulty:** Easy
+**Topics:** Array, Hash Table, Divide and Conquer, Sorting, Counting
+**Tags:** grind-75
+
+**LeetCode:** [Problem 169](https://leetcode.com/problems/majority-element/description/)
+
+## Problem Description
+
+Given an array `nums` of size `n`, return the majority element.
+
+The majority element is the element that appears more than `⌊n / 2⌋` times. You may assume that the majority element always exists in the array.
+
+## Examples
+
+### Example 1:
+
+```
+Input: nums = [3,2,3]
+Output: 3
+```
+
+### Example 2:
+
+```
+Input: nums = [2,2,1,1,1,2,2]
+Output: 2
+```
+
+## Constraints
+
+- n == nums.length
+- 1 <= n <= 5 \* 10^4
+- -10^9 <= nums[i] <= 10^9
+
+**Follow-up:** Could you solve the problem in linear time and in O(1) space?

leetcode/majority_element/__init__.py

@@ -0,0 +1,79 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "imports",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from solution import Solution"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "setup",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Example test case\n",
+    "nums = [3, 2, 3]\n",
+    "expected = 3"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "id": "execute",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "3"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "result = Solution().majority_element(nums)\n",
+    "result"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "id": "test",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "assert result == expected"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "leetcode-py-py3.13",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.13.7"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

leetcode/majority_element/playground.ipynb

@@ -0,0 +1,14 @@
+class Solution:
+    # Time: O(n)
+    # Space: O(1)
+    def majority_element(self, nums: list[int]) -> int:
+        # Boyer-Moore Voting Algorithm
+        candidate = 0
+        count = 0
+
+        for num in nums:
+            if count == 0:
+                candidate = num
+            count += 1 if num == candidate else -1
+
+        return candidate

leetcode/majority_element/solution.py

@@ -0,0 +1,19 @@
+import pytest
+
+from leetcode_py.test_utils import logged_test
+
+from .solution import Solution
+
+
+class TestMajorityElement:
+    def setup_method(self):
+        self.solution = Solution()
+
+    @pytest.mark.parametrize(
+        "nums, expected",
+        [([3, 2, 3], 3), ([2, 2, 1, 1, 1, 2, 2], 2), ([1], 1), ([1, 1, 2], 1), ([2, 2, 2, 1, 1], 2)],
+    )
+    @logged_test
+    def test_majority_element(self, nums: list[int], expected: int):
+        result = self.solution.majority_element(nums)
+        assert result == expected