reverse-words-in-a-string-iii.py

# Time:  O(n)
# Space: O(1)

# Given a string, you need to reverse the order of characters in each word within a sentence
# while still preserving whitespace and initial word order.
#
# Example 1:
# Input: "Let's take LeetCode contest"
# Output: "s'teL ekat edoCteeL tsetnoc"
# Note: In the string, each word is separated by single space and
# there will not be any extra space in the string.

class Solution(object):
    def reverseWords(self, s):
        """
        :type s: str
        :rtype: str
        """
        def reverse(s, begin, end):
            for i in xrange((end - begin) // 2):
                s[begin + i], s[end - 1 - i] = s[end - 1 - i], s[begin + i]

        s, i = list(s), 0
        for j in xrange(len(s) + 1):
            if j == len(s) or s[j] == ' ':
                reverse(s, i, j)
                i = j + 1
        return "".join(s)