Add 'Merge Strings Alternately'

Author: nickolashkraus

README.md

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

src/merge_strings_alternately.py

@@ -0,0 +1,41 @@
+"""
+1768. Merge Strings Alternately
+
+https://leetcode.com/problems/merge-strings-alternately
+
+NOTES
+  * Simple two pointer algorithm.
+
+Slight optimization: You don't actually need the variable `i`.
+
+  ```
+  res += word1[p1] + word2[p2]
+  p1 += 1
+  p2 += 1
+  ```
+"""
+
+
+class Solution:
+    def mergeAlternately(self, word1: str, word2: str) -> str:
+        p1, p2, i = 0, 0, 0
+        res = ""
+
+        while p1 < len(word1) and p2 < len(word2):
+            if i % 2 == 0:
+                res += word1[p1]
+                p1 += 1
+            else:
+                res += word2[p2]
+                p2 += 1
+            i += 1
+
+        while p1 < len(word1):
+            res += word1[p1]
+            p1 += 1
+
+        while p2 < len(word2):
+            res += word2[p2]
+            p2 += 1
+
+        return res

tests/test_merge_strings_alternately.py

@@ -0,0 +1,23 @@
+"""
+1768. Merge Strings Alternately
+
+https://leetcode.com/problems/merge-strings-alternately
+"""
+
+from unittest import TestCase
+
+from src.merge_strings_alternately import Solution
+
+
+class TestSolution(TestCase):
+    def test_1(self):
+        exp = "apbqcr"
+        assert Solution().mergeAlternately("abc", "pqr") == exp
+
+    def test_2(self):
+        exp = "apbqrs"
+        assert Solution().mergeAlternately("ab", "pqrs") == exp
+
+    def test_3(self):
+        exp = "apbqcd"
+        assert Solution().mergeAlternately("abcd", "pq") == exp