leetode 169

Author: Kondareddy1209

Leetcode/Leetcode_169.py

@@ -0,0 +1,96 @@
+"""
+Problem: Majority Element
+
+Given an array nums of size n, return the majority element.
+The majority element is the element that appears more than ⌊n/2⌋ times.
+
+Approach:
+- Use a dictionary (hash map) to count the frequency of each element.
+- Return the element with the maximum frequency.
+
+Example:
+Input: nums = [1, 2, 1, 1, 3, 2, 1]
+Output: 1
+"""
+
+from typing import List
+
+
+class Solution:
+    def majorityElement(self, nums: List[int]) -> int:
+        """
+        Finds the majority element in the list.
+
+        Steps:
+        1. Create a dictionary to store frequencies.
+        2. Traverse the list and update counts.
+        3. Find the element with maximum frequency.
+        4. Return that element.
+        """
+
+        # Step 1: Initialize dictionary
+        freq = {}
+
+        # Step 2: Count frequencies
+        for num in nums:
+            if num in freq:
+                freq[num] += 1
+            else:
+                freq[num] = 1
+
+        # Step 3: Find element with highest frequency
+        majority = max(freq, key=freq.get)
+
+        # Step 4: Return result
+        return majority
+
+
+# -------------------- Execution Example --------------------
+if __name__ == "__main__":
+    nums = [1, 2, 1, 1, 3, 2, 1]
+
+    solution = Solution()
+    result = solution.majorityElement(nums)
+
+    print("Input:", nums)
+    print("Majority Element:", result)
+
+
+"""
+Execution Walkthrough:
+
+nums = [1, 2, 1, 1, 3, 2, 1]
+
+Building frequency dictionary:
+1 → {1:1}
+2 → {1:1, 2:1}
+1 → {1:2, 2:1}
+1 → {1:3, 2:1}
+3 → {1:3, 2:1, 3:1}
+2 → {1:3, 2:2, 3:1}
+1 → {1:4, 2:2, 3:1}
+
+max(freq, key=freq.get) → 1
+
+Output:
+Majority Element: 1
+"""
+
+
+"""
+Time Complexity (T.C.):
+- Traversing array: O(n)
+- Finding max: O(n)
+Overall: O(n)
+
+Space Complexity (S.C.):
+- Dictionary storage: O(n)
+Overall: O(n)
+"""
+
+
+"""
+Notes:
+- Easy and intuitive solution using hashing.
+- For interviews, also learn Boyer-Moore Voting Algorithm (O(1) space).
+"""