leetcode 88

Author: Kondareddy1209

Leetcode/Leetcode_88.py

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+"""
+LeetCode Problem: 88. Merge Sorted Array
+
+Problem Statement:
+You are given two sorted integer arrays nums1 and nums2, and two integers m and n.
+
+- nums1 has a size of m + n, where:
+  - first m elements are valid
+  - last n elements are 0 (empty space)
+
+- nums2 has n elements
+
+Merge nums2 into nums1 as one sorted array (in-place).
+
+--------------------------------------------------
+
+Example:
+Input:
+nums1 = [1,2,3,0,0,0], m = 3
+nums2 = [2,5,6], n = 3
+
+Output:
+[1,2,2,3,5,6]
+
+--------------------------------------------------
+
+Approach (Your Method - Fill + Sort):
+
+1. Fill nums2 elements into nums1 starting from index m
+2. Sort nums1 to get the final merged sorted array
+
+--------------------------------------------------
+
+Dry Run:
+
+nums1 = [1,2,3,0,0,0]
+nums2 = [2,5,6]
+
+Step 1: Fill nums2 into nums1
+→ nums1 = [1,2,3,2,5,6]
+
+Step 2: Sort nums1
+→ nums1 = [1,2,2,3,5,6]
+
+--------------------------------------------------
+
+Time Complexity:
+O((m+n) log(m+n)) → due to sorting
+
+Space Complexity:
+O(1) → in-place modification
+
+--------------------------------------------------
+
+Key Learnings:
+- Understand difference between actual values and placeholder zeros
+- In-place modification is important
+- This approach is simple but not optimal
+- Optimal solution uses 3 pointers (O(m+n))
+
+--------------------------------------------------
+"""
+
+from typing import List
+
+
+class Solution:
+    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
+        # k → pointer for nums2
+        k = 0
+
+        # Fill nums2 elements into nums1 after index m
+        for l in range(len(nums1)):
+            if l >= m:
+                nums1[l] = nums2[k]
+                k += 1
+
+        # Sort the merged array
+        nums1.sort()
+
+
+# ------------------------------
+# Example Run (for testing)
+# ------------------------------
+if __name__ == "__main__":
+    nums1 = [1, 2, 3, 0, 0, 0]
+    m = 3
+    nums2 = [2, 5, 6]
+    n = 3
+
+    sol = Solution()
+    sol.merge(nums1, m, nums2, n)
+
+    print("Merged Array:", nums1)