151. Reverse Words in a String

Given an input string, reverse the string word by word.For example,
Given s = "

the sky is blue

",
return "

blue is sky the

".Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.click to show clarification.Clarification:What constitutes a word?
A sequence of non-space characters constitutes a word.
Could the input string contain leading or trailing spaces?
Yes. However, your reversed string should not contain leading or trailing spaces.
How about multiple spaces between two words?
Reduce them to a single space in the reversed string.
本题较为复杂，主要在于可能会存在前缀或者多个连在一起的空格，此时要删去多余的空格，这就需要我们用一个cur指针指向新数组的遍历位置，然后一个一个往前复制。
反转可以分为两步，第一步先将整个数组反转，第二步为将每个单词单独反转，则可得到结果。

class Solution {
public:
void reverseWords(string &s) {
int cur=0;
reverse(s.begin(),s.end());
for(int i=0;i<s.size();i++)
{
if(s[i]==' ')
continue;
if(cur!=0)
s[cur++]=' ';
int j=i;
while(j<s.size()&&s[j]!=' ')
s[cur++]=s[j++];
reverse(s.begin()+cur-(j-i),s.begin()+cur);
i=j;
}
s.resize(cur);
}
};