Given a string containing opening braces '(' and closing braces ')' find the index where you have the same number of opening and closing braces

brackets_equilibrium.py

# Codility challenge
# Given a string containing opening braces '(' and closing braces ')'
# Return the index where you have the same number of opening and closing braces
# Example:
#   Given '(())' the equilibrium index is two because there are the same number
#   of opening brackets to the left as there are closing brackets to the right
#
#   Given '(((' the equilibrium index is 0 because there are no opening brackets
#   before index 0 and there are 0 closing brackets at that position
#
#   Given '))' the equilibrium index is 2 because at position two there are no
#   closing brackets to the right and no opening brackets to the left
#
#   Given '((()(' the equilibrium  index is 1

# This one is easy. Consists on finding the index where the brackets are in a equilibrium.
# We can do the naive way with two loops. But we will be doing the less naive version
# By storing how many opening and closing braces are at each point.
# This can be done with a dictionary or just a couple of lists/arrays
def solution(S):
    
    # This variables will be used to keep track of how many opening or closing
    # braces we have ran in. We can do without these by using the value to the
    # left or right respectively. Just here for clarity.
    soFarLeft = 0
    soFarRight = 0
    # The data structures that will hold how many brackets we've found so far
    lefts = [0] * len(S)
    rights = [0] * len(S)
    
    # No opening braces before the first element
    lefts.insert(0, 0)
    # No closing braces after the last element
    rights.append(0)
    
    for leftIndex in range(1, len(S)+1):
        
        rightIndex = len(S) - leftIndex
        
        if S[leftIndex-1] == '(':
            soFarLeft += 1
        
        if S[rightIndex] == ')':
            soFarRight += 1
            
        lefts[leftIndex] = soFarLeft
        rights[rightIndex] = soFarRight
        
    print lefts
    print rights
                
    for index, (left, right) in enumerate(zip(lefts, rights)):
        if left == right:
            return index
    
    return result