給出一個0-1字符串，問最少操作幾次可以將字符串變為....0-1-0-1....用兩個計數器記錄首位取0和取1分別要操作幾次，取兩者較小值
#1758
#Runtime: 25 ms (Beats 79.41%)
#Memory: 13.4 MB (Beats 88.24)
class Solution(object):
def minOperations(self, s):
"""
:type s: str
:rtype: int
"""
ans1, ans2 = 0, 0
for i in xrange(0, len(s)):
if i % 2:
if s[i] == '0':
ans1 += 1
else:
ans2 += 1
else:
if s[i] == '1':
ans1 += 1
else:
ans2 += 1
return min(ans1, ans2)