[LeetCode]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".

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思考：一开始没有考虑空格。去掉不合法空格+两次翻转，不需要额外空间。

class Solution {

public:

    void reverseWords(string &s) {

        int len=s.length();

        int i=0,j=len-1;

        //去掉前后空格

        while(i<len&&s[i]==' ') i++;

        while(j>=0&&s[j]==' ') j--;	

        len=j-i+1;

        s=s.substr(i,len);

        //去掉中间空格

        for(i=0;i<s.length();i++)

        {

            if(s[i]==' ')

			{

				j=i+1;

				while(s[j]==' ') j++;

				s.erase(i+1,j-i-1);

			}

        }

        len=s.length();

        for(i=0;i<len/2;i++) swap(s[i],s[len-i-1]);

        int start=0;

        for(i=0;i<=len;i++)

        {

            if((i<len&&s[i]==' ')||i==len)

            {

                for(j=start;j<(i+start)/2;j++) swap(s[j],s[i-(j-start)-1]);

				start=i+1;

            }

        }

    }

};