Check if a string is rotation of another WITHOUT concatenating

Question

There are 2 strings , how can we check if one is a rotated version of another ?

For Example : hello --- lohel

One simple solution is by co

Answer 1

There's no need to concatenate at all.

First, check the lengths. If they're different then return false.

Second, use an index that increments from the first character to the last of the source. Check if the destination starts with all the letters from the index to the end, and ends with all the letters before the index. If at any time this is true, return true.

Otherwise, return false.

EDIT:

An implementation in Python:

def isrot(src, dest):
  # Make sure they have the same size
  if len(src) != len(dest):
    return False

  # Rotate through the letters in src
  for ix in range(len(src)):
    # Compare the end of src with the beginning of dest
    # and the beginning of src with the end of dest
    if dest.startswith(src[ix:]) and dest.endswith(src[:ix]):
      return True

  return False

print isrot('hello', 'lohel')
print isrot('hello', 'lohell')
print isrot('hello', 'hello')
print isrot('hello', 'lohe')