Reverse Words in a String II

第一题的原理不借助内建函数实现一下就好了，所有词自己反转一遍，再把整个数组反转一遍

class Solution:
    # @param s, a list of 1 length strings, e.g., s = ['h','e','l','l','o']
    # @return nothing
    def reverseWords(self, s):
        pre = 0
        n = len(s)

        for i in xrange(n):
            if s[i] == ' ':
                self.reverse(s, pre, i - 1)
                pre = i + 1

        self.reverse(s, pre, n - 1)
        s.reverse()

    def reverse(self, string, start, end):
        while start < end:
            string[start], string[end] = string[end], string[start]
            start += 1
            end -= 1