4.rotate an array and test case

Author: PTHARRISH

geek_for_geeks/challenge/rotate_an_array.py

@@ -0,0 +1,62 @@
+# 4.rotate an array
+# Reversal Algorithm(best approach)
+def rotateArr(arr, d):
+    n = len(arr)
+    d %= n
+
+    def reversal(arr, start, end):
+        while start < end:
+            arr[start], arr[end] = arr[end], arr[start]
+            start += 1
+            end -= 1
+        return arr
+
+    reversal(arr, 0, d - 1)
+    reversal(arr, d, n - 1)
+    reversal(arr, 0, n - 1)
+    return arr
+
+
+# T.C = O(n)
+# S.C = O(1)
+
+
+def rotateArr(arr, d):
+    n = len(arr)
+    d = d % n
+    return arr[d:] + arr[:d]
+
+
+# T.C = O(n)
+# S.C = O(n)
+
+
+def rotateArr(arr, d):
+    n = len(arr)
+    temp = []
+    for i in range(d, n):
+        temp.append(arr[i])
+    for j in range(0, d):
+        temp.append(arr[j])
+    return temp
+
+
+# T.C = O(n)
+# S.C = O(n)
+
+
+def rotateArr(arr, d):
+    n = len(arr)
+    first = 0
+    for i in range(d):
+        first = arr[0]
+        for j in range(n - 1):
+            arr[j] = arr[j + 1]
+        arr[n - 1] = first
+    return arr
+
+
+# T.C = O(d*n)
+# S.C = O(1)
+
+print(rotateArr([1, 2, 3, 4, 5], 2))

test/test_case.py

@@ -4,6 +4,7 @@
 sys.path.append(os.path.abspath(".."))
 from geek_for_geeks.challenge.move_zero import pushZerosToEnd
 from geek_for_geeks.challenge.reverse_an_array import reverseArray
+from geek_for_geeks.challenge.rotate_an_array import rotateArr
 from geek_for_geeks.challenge.secondlargest import getSecondLargest
 
 
@@ -93,3 +94,25 @@ def test_palindrome_list(self):
         arr = [1, 2, 3, 2, 1]
         expected = [1, 2, 3, 2, 1]
         assert reverseArray(arr) == expected
+
+
+class TestRotateArr:
+    def test_rotate_by_two(self):
+        arr = [1, 2, 3, 4, 5]
+        rotated = rotateArr(arr, 2)
+        assert rotated == [3, 4, 5, 1, 2]
+
+    def test_rotate_by_zero(self):
+        arr = [1, 2, 3]
+        rotated = rotateArr(arr, 0)
+        assert rotated == [1, 2, 3]
+
+    def test_rotate_by_length(self):
+        arr = [1, 2, 3]
+        rotated = rotateArr(arr, 3)
+        assert rotated == [1, 2, 3]
+
+    def test_rotate_by_more_than_length(self):
+        arr = [1, 2, 3, 4]
+        rotated = rotateArr(arr, 6)  # 6 % 4 = 2
+        assert rotated == [3, 4, 1, 2]