LeetCode OJ - Reverse Words in a String

class Solution {
public:
    void swap(char& a, char& b){
        int tmp = a;
        a = b;
        b = tmp;
    }
    void reverse(string &s, int begin, int end){
        if (s[begin] == ‘\0‘ || s[end] == ‘\0‘){
            return;
        }
        while (begin < end){
            swap(s[begin], s[end]);
            begin++;
            end--;
        }
    }
    void reverseWords(string &s) {
        if (s[0] == ‘\0‘ || s.empty()){
            return;
        }
        reverse(s, 0, s.length() - 1);
        //*/
        int start = 0, end = 0, len = 0;
        while (start < s.length()){
            while (start != s.length() && s[start] == ‘ ‘) start++; //跳过对于的空格
            for (end = start; end != s.length() && s[end] != ‘ ‘; end++);
            if (len != 0 && end > start) s[len++] = ‘ ‘;
            if (end > start){
                reverse(s, start, end - 1);
            }
            while (start < end) s[len++] = s[start++];
            
        }
        s.resize(len);
        //*/
    }
};