Add gcd task

Author: onixlas

array-string/1071_greatest_common_divisor_of_strings/solution.py

@@ -0,0 +1,15 @@
+class Solution:
+    def gcdOfStrings(self, str1: str, str2: str) -> str:
+        length1, length2 = len(str1), len(str2)
+
+        def is_valid_gcd(index):
+            if length1 % index or length2 % index:
+                return False
+            n1, n2 = length1 // index, length2 // index
+            base = str1[:index]
+            return str1 == n1 * base and str2 == n2 * base
+
+        for i in range(min(length1, length2), 0, -1):
+            if is_valid_gcd(i):
+                return str1[:i]
+        return ""