Python3 Program for Reversal algorithm for right rotation of an array
Given an array, right rotate it by k elements.
After K=3 rotation
Examples:
Input: arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} k = 3 Output: 8 9 10 1 2 3 4 5 6 7 Input: arr[] = {121, 232, 33, 43 ,5} k = 2 Output: 43 5 121 232 33
Note : In the below solution, k is assumed to be smaller than or equal to n. We can easily modify the solutions to handle larger k values by doing k = k % n
Algorithm:
rotate(arr[], d, n) reverseArray(arr[], 0, n-1) ; reverse(arr[], 0, d-1); reverse(arr[], d, n-1);
Below is the implementation of above approach:
Python3
# Python3 program for right rotation of # an array (Reversal Algorithm) # Function to reverse arr # from index start to end def reverseArray( arr, start, end): while (start < end): arr[start], arr[end] = arr[end], arr[start] start = start + 1 end = end - 1 # Function to right rotate arr # of size n by d def rightRotate( arr, d, n): reverseArray(arr, 0 , n - 1 ); reverseArray(arr, 0 , d - 1 ); reverseArray(arr, d, n - 1 ); # function to print an array def printArray( arr, size): for i in range ( 0 , size): print (arr[i], end = ' ' ) # Driver code arr = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ] n = len (arr) k = 3 # Function call rightRotate(arr, k, n) printArray(arr, n) # This article is contributed # by saloni1297 |
Output:
8 9 10 1 2 3 4 5 6 7
Time Complexity: O(N)
Auxiliary Space: O(1)
Please refer complete article on Reversal algorithm for right rotation of an array for more details!