每日一题 151. Reverse Words in a String

自己写的

class Solution {
public:
    string reverseWords(string s) {
        vector<string> words;
        int i = 0;
        while(s[i] == ' ' && i < s.length()){
            i++;
        }
        while(i < s.length()){
            string temp = "";
            while(s[i] != ' ' && i < s.length()){
                temp += s[i];
                i++;
            }
            words.push_back(temp);
            while(s[i] == ' ' && i < s.length()){
                i++;
            }
        }
        reverse(words.begin(), words.end());//实际上不需要这一步，反过来输出就行
        string res = "";
        for(string word : words){
            res += word;
            res += " ";
        }
        res = res.substr(0, res.length()-1);
        return res;
    }
};

如果想原字符数改，可以先去除头尾空格，然后字符串翻转，再翻转每一个单词
更简单的写法

class Solution {
public:
    string reverseWords(string s) {
        
        vector<string> temp;
        
		// initializing stringstream object
        stringstream str(s);
        
        string words;
        
		// storing each words in a vector
        while(str >> words)
            temp.push_back(words);
        
        reverse(temp.begin(), temp.end());
        
        string ans;
        
		// storing character by character each word in reverse order
        for(auto it : temp)
        {
            for(auto c : it)
                ans.push_back(c);
            
            ans.push_back(' ');
        }
        
		// deleting extra space
        ans.pop_back();
        
        return ans;
    }
};