leetcode Reverse Words in a String

class Solution {
public:
	void reverseWords(string &s) {
	    del_tail_blank(s);
		reverse(s.begin(), s.end());
        del_tail_blank(s);
		string word;
		for (auto start = s.begin(); start != s.end();){
		    auto end = start;
		    for (; end != s.end() && *end != ' '; ++end);
		    reverse(start, end); //start依然对应的是头，end 依然对应的是尾，只是指针所指向的值变了
		    start = end;
		    if (end != s.end()){
		        start = ++end; // 跳过一个空格
		        for (; end != s.end() && *end == ' '; ++end);
		        start = s.erase(start, end); // start = end
		    }
		}
	}
private:
    void del_tail_blank(string &s){
        int i;
        for (i = s.size() - 1; i >= 0 && s[i] == ' '; --i);
        s.erase(++i, s.size() - i);
    }
};