Add 'Merge Sorted Array'

Author: nickolashkraus

README.md

@@ -58,6 +58,8 @@ A collection of LeetCode solutions
 
 [Merge k Sorted Lists](./src/merge_k_sorted_lists.py)
 
+[Merge Sorted Array](./src/merge_sorted_array.py)
+
 [Merge Strings Alternately](./src/merge_strings_alternately.py)
 
 [Merge Two Sorted Lists](./src/merge_two_sorted_lists.py)

src/merge_sorted_array.py

@@ -0,0 +1,43 @@
+"""
+88. Merge Sorted Array
+
+https://leetcode.com/problems/merge-sorted-array
+
+NOTES
+  * Use three pointer merge algorithm.
+
+The fact that the first array, `nums1`, has additional space (n) should signify
+that the problem can be solved without additional space. Since both arrays are
+already sorted, only an O(m + n) traversal is required to merge them. By
+starting the traversal from m - 1 and n - 1 of `nums1` and `nums2`,
+respectively, and by leveraging the additional space appended to `nums1`, the
+arrays can be merged in-place without the need for additional space.
+"""
+
+
+class Solution:
+    def merge(self, nums1: list[int], m: int, nums2: list[int], n: int) -> None:
+        """
+        Do not return anything, modify nums1 in-place instead.
+        """
+        p1, p2, p3 = m - 1, n - 1, m + n - 1
+
+        while p1 >= 0 and p2 >= 0:
+            if nums1[p1] >= nums2[p2]:
+                nums1[p3] = nums1[p1]
+                p1 -= 1
+                p3 -= 1
+            else:
+                nums1[p3] = nums2[p2]
+                p2 -= 1
+                p3 -= 1
+
+        while p1 >= 0:
+            nums1[p3] = nums1[p1]
+            p1 -= 1
+            p3 -= 1
+
+        while p2 >= 0:
+            nums1[p3] = nums2[p2]
+            p2 -= 1
+            p3 -= 1

tests/test_merge_sorted_array.py

@@ -0,0 +1,35 @@
+"""
+88. Merge Sorted Array
+
+https://leetcode.com/problems/merge-sorted-array
+"""
+
+from unittest import TestCase
+
+from src.merge_sorted_array import Solution
+
+
+class TestSolution(TestCase):
+    def test_1(self):
+        exp = [1, 2, 2, 3, 5, 6]
+        nums1, nums2 = [1, 2, 3, 0, 0, 0], [2, 5, 6]
+        Solution().merge(nums1, 3, nums2, 3)
+        assert nums1 == exp
+
+    def test_2(self):
+        exp = [1]
+        nums1, nums2 = [1], []
+        Solution().merge(nums1, 1, nums2, 0)
+        assert nums1 == exp
+
+    def test_3(self):
+        exp = [1]
+        nums1, nums2 = [0], [1]
+        Solution().merge(nums1, 0, nums2, 1)
+        assert nums1 == exp
+
+    def test_4(self):
+        exp = [1, 2, 3, 4, 5, 6]
+        nums1, nums2 = [4, 5, 6, 0, 0, 0], [1, 2, 3]
+        Solution().merge(nums1, 3, nums2, 3)
+        assert nums1 == exp