LeetCode: 151. Reverse Words in a String

题目描述

Given an input string, reverse the string word by word.

Example:

Input: "the sky is blue",
Output: "blue is sky the".

Note:

A word is defined as a sequence of non-space characters.
Input string may contain leading or trailing spaces. 
However, your reversed string should not contain leading or trailing spaces.
You need to reduce multiple spaces between two words to a single space in the reversed string.

解题思路

获取用空格分割开的单词，然后将他们的倒序插入结果串中。

AC 代码

class Solution {
public:
    void reverseWords(string &s) {
        string ans;
        int lastPos = s.find_first_not_of(' ');
        int curPos = s.find_first_of(' ', lastPos);

        while(lastPos != s.npos)
        {    
            if(curPos == s.npos) curPos = s.size();

            if(!ans.empty()) ans = " " + ans;
            ans = s.substr(lastPos, curPos - lastPos) + ans;

            lastPos = s.find_first_not_of(' ', curPos);
            curPos = s.find_first_of(' ', lastPos);
        }

        s = ans;
    }
};