Added optimized solution for #197

Solutions/197.py

@@ -20,16 +20,55 @@ def rotate_array_right(arr: List[int], k: int) -> List[int]:
     return arr
 
 
+def rotate_array_right_optimized(arr: List[int], k: int) -> List[int]:
+    length = len(arr)
+    k = k % length
+    if k > 0:
+        iteration_start_idx = 0
+        moves_remaining = length
+        while moves_remaining:
+            # Rotate the element at iteration_start_idx, and every kth element thereafter including looping around as needed, k places right
+            # First, memorize the element at iteration_start_idx
+            iteration_start_elem = arr[iteration_start_idx]
+            curr_idx = (iteration_start_idx - k) % length
+            # Rotate the appropriate element into its place...then one into that one's place...etc.
+            while curr_idx != iteration_start_idx:
+                arr[(curr_idx + k) % length] = arr[curr_idx]
+                moves_remaining -= 1
+                curr_idx -= k
+                curr_idx %= length
+            # Finally, place the element origianlly at iteration_start_idx in its appropriate new location
+            arr[(iteration_start_idx + k) % length] = iteration_start_elem
+            moves_remaining -= 1
+            # Move onto the next group of length/gcd(length, k) elements
+            iteration_start_idx += 1
+    return arr
+
+
 if __name__ == "__main__":
-    print(rotate_array_right([(i + 1) for i in range(5)], 9))
-    print(rotate_array_right([(i + 1) for i in range(5)], 3))
-    print(rotate_array_right([(i + 1) for i in range(5)], 2))
-    print(rotate_array_right([(i + 1) for i in range(5)], 1))
+    for arr, k in [
+        ([(i + 1) for i in range(5)], 9),
+        ([(i + 1) for i in range(5)], 3),
+        ([(i + 1) for i in range(5)], 2),
+        ([(i + 1) for i in range(5)], 1),
+        ([(i + 1) for i in range(5)], 0),
+        ([(i + 1) for i in range(5)], 5),
+        ([(i + 1) for i in range(10)], 4),
+        ([(i + 1) for i in range(15)], 4),
+    ]:
+        arr_copy = arr[:]
+        print(rotate_array_right(arr, k))
+        print(rotate_array_right_optimized(arr_copy, k))
 
 
 """
 SPECS:
 
-TIME COMPLEXITY: O(n ^ 2)
+rotate_array_right:
+TIME COMPLEXITY: originally said O(n ^ 2); in fact seeems O(n)
 SPACE COMPLEXITY: O(n)
+
+rotate_array_right_optimized:
+TIME COMPLEXITY: O(n)
+SPACE COMPLEXITY: O(1) (auxiliary)
 """