力扣151. 反转字符串中的单词

class Solution {
public:
    void reverse(string& s, int start, int end) {
        for(; start < end; start++, end--) {
            swap(s[start], s[end]);
        }
    }

    void removeSpace(string& s) {
        int slow = 0;
        for(int fast = 0; fast < s.size(); fast++) {
            if(s[fast] == ' ') continue;
            if(slow != 0) s[slow++] = ' ';
            while(fast < s.size() && s[fast] != ' ') {
                s[slow++] = s[fast++];
            }
        }
        s.resize(slow);
    }

    string reverseWords(string s) {
        removeSpace(s);
        reverse(s, 0, s.size() - 1);
        int start = 0;
        for(int i = 0; i <= s.size(); i++) {
            if(s[i] == ' ' || i == s.size()) {
                reverse(s, start, i - 1);
                start = i + 1;
            }
        }
        return s;
    }
};