[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".
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.

代码很简单：

从头向尾扫描s：

如果当前字符是space，而且buffer string 不为空，那么输出buffer string。

如果当前字符是space，而且buffer string为空，那么不输出buffer string。

如果当前字符不是space，那么把当前字符添加到buffer string。

class Solution {public:    void reverseWords(string &s) {        string word; //tmp string to store each word        string res; // result string        int i=0;        while (i<s.size()){            if (char(s[i])==' ' && word.empty()){i++;continue;} //multiple spaces            if (char(s[i])==' ' && !word.empty()){ //first space after a word                res = word+" "+ res; //store the word                word=""; //reset the word                i++; continue;            }            if (char(s[i])!=' '){word=word+char(s[i]);i++; continue;} //non-space chars         }                if (!word.empty()){ //last word            s = word+" "+res;        }else{            s = res;        }        s = s.substr(0,s.size()-1); //eliminate the last space    }    };