We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
Loading...
  1. Practice
  2. Tutorials
  3. Cracking the Coding Interview
  4. Arrays: Left Rotation
  5. Discussions

Arrays: Left Rotation

  • aniket_vartak + 1 comment

    you dont need to pass n to your function, right..

    • michael_bubb + 2 comments

      I agree - I ended up not using 'n' (Python):

      def left_shift(n,k,a):
   for _ in range(k):
      a.append(a.pop(0))
   print(*a)
      • unitraxx + 1 comment

        Obviously this solves the problem, but is a terrible solution. Pop is an O(N) operation. So your solution becomes O(K*N). This should be done in O(N) total time complexity. You do have the space requirement of O(1) correct. All the standard solutions have a O(N) space complexity.

        • asfaltboy + 1 comment

          True. However, it becomes an elegant solution if we use collections.dequeue instead of list. Double ended queues have a popleft method, which is an O(1) operation:

          def array_left_rotation(a, n, k):
    for _ in range(k):
        a.append(a.popleft())
    return a

          More info: https://wiki.python.org/moin/TimeComplexity#collections.deque https://docs.python.org/3/library/collections.html#collections.deque

          • AffineStructure + 1 comment

            They have rotate built into the deque

            def array_left_rotation(a, n, k):
    a = deque(a)
    for i in range(k):
        a.rotate(-1)
    return a
            • josegabriel_st + 0 comments

              You have O(n) in:

              a = deque(a)

              In order to avoid this, you should use a deque from the beginning like:

              from collections import deque

def array_left_rotation(a, n, k):
    a.rotate(-k)

n, k = map(int, input().strip().split(' '))
a = deque(map(int, input().strip().split(' ')))
array_left_rotation(a, n, k);
print(*a, sep=' ')

              And array_left_rotation only takes O(k) instead of O(n).

              Note that a is pased by reference, so there is no need to return anything, but this could be an issue for some user cases, for this particular problem, it works.

      • navi_srm + 0 comments

        def array_left_rotation(a, n, k): return (a[k:] + a[:k])