LeetCode: Reverse Words in a String

先来一个需要extra space的

class Solution {
public:
    void reverseWords(string &s) {
        vector<string> S;
        int pre = 0;
        string tmp = "";
        for (int i = 0; i < s.size(); ++i) {
            if (isspace(s[i]) && tmp.size()) {
                S.push_back(tmp);
                tmp.clear();
            }
            else if (!isspace(s[i])) tmp += s[i];
        }
        if (tmp.size()) S.push_back(tmp);
        s.clear();
        for (int i = S.size()-1; i >= 0; --i) {
            if (i == S.size() - 1) s += S[i];
            else s = s + " " + S[i];
        }
    }
};

再来个更好的

class Solution {
public:
    void reverseWords(string &s) {
        string rs;
        for (int i = s.size()-1; i >= 0; ) {
            while (i >= 0 && isspace(s[i])) i--;
            if (i < 0) break;
            if (rs.size()) rs += " ";
            string t;
            while(i >= 0 && !isspace(s[i])) t += s[i--];
            int left = 0;
            int right = t.size()-1;
            while (left < right) swap(t[left++], t[right--]);
            rs += t;
        }
        s = rs;
    }
};