LeetCode: Reverse Words in a String

先来一个需要extra space的

 1 class Solution {
 2 public:
 3     void reverseWords(string &s) {
 4         vector<string> S;
 5         int pre = 0;
 6         string tmp = "";
 7         for (int i = 0; i < s.size(); ++i) {
 8             if (isspace(s[i]) && tmp.size()) {
 9                 S.push_back(tmp);
10                 tmp.clear();
11             }
12             else if (!isspace(s[i])) tmp += s[i];
13         }
14         if (tmp.size()) S.push_back(tmp);
15         s.clear();
16         for (int i = S.size()-1; i >= 0; --i) {
17             if (i == S.size() - 1) s += S[i];
18             else s = s + " " + S[i];
19         }
20     }
21 };

再来个更好的

 1 class Solution {
 2 public:
 3     void reverseWords(string &s) {
 4         string rs;
 5         for (int i = s.size()-1; i >= 0; ) {
 6             while (i >= 0 && isspace(s[i])) i--;
 7             if (i < 0) break;
 8             if (rs.size()) rs += " ";
 9             string t;
10             while(i >= 0 && !isspace(s[i])) t += s[i--];
11             int left = 0;
12             int right = t.size()-1;
13             while (left < right) swap(t[left++], t[right--]);
14             rs += t;
15         }
16         s = rs;
17     }
18 };