每日算法题: Fix Brackets

Hi, here's your problem today. This problem was recently asked by Twitter:

Given a string with only ( and ), find the minimum number of characters to add or subtract to fix the string such that the brackets are balanced.

Example:
Input: '(()()'
Output: 1
Explanation:

The fixed string could either be ()() by deleting the first bracket, or (()()) by adding a bracket. These are not the only ways of fixing the string, there are many other ways by adding it in different positions!


Here's some code to start with:

def fix_brackets(s):
# Fill this in.

print fix_brackets('(()()')
# 1