##### Short Problem Definition:

Find a symmetry point of a string, if any.

##### Link

##### Complexity:

expected worst-case time complexity is O(length(S));

expected worst-case space complexity is O(1) (not counting the storage required for input arguments).

##### Execution:

This problem gave me a lot of headache. It is so trivial I that over-complicated it. I thoughtÂ that you should find a symmetry point at any possible position, ignoring the residual characters. You would obviously try to maximize the length of this symmetrical sub-array. I was not able to come with any O(S) algorithm for this problem derivation. So just to remind you,** this problem is a simple palindrome check**. Additionally, you drop all evenly sized strings as their symmetry point is between the indexes.

##### Solution:

def solution(S): l = len(S) if l % 2 == 0: return -1 mid_point = l // 2 for idx in xrange(0, mid_point): if S[idx] != S[l - idx - 1]: return -1 return mid_point

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