剑指 Offer 58 - I. 翻转单词顺序

class Solution {
   public:
    string reverseWords(string s) {
        int n = s.size();
        string ans = "";
        for (int i = n - 1; i >= 0; i--) {
            if (s[i] != ' ') {
                int j = i;
                while (i >= 0 && s[i] != ' ') {
                    i--;
                }
                ans.append(s.substr(i + 1, j - i) + " ");
            }
        }
        return ans.substr(0, ans.size() - 1);
    }
};