LeetCode: Word Break II

难题

 

 1 class Solution {

 2 public:

 3     void dfs(string s, vector<string> &tmp, vector<string> &res, unordered_set<string> &unused, unordered_set<string> &dict) {

 4         if (s.size() == 0) {

 5             string ans = "";

 6             for (int i = 0; i < tmp.size(); i++) {

 7                 if (i == 0) ans += tmp[i];

 8                 else ans += " " + tmp[i];

 9             }

10             res.push_back(ans);

11             return;

12         }

13         if (unused.find(s) != unused.end()) return;

14         int pre = res.size();

15         for (int i = 1; i <= s.size(); i++) {

16             if (dict.find(s.substr(0, i)) != dict.end()) {

17                 tmp.push_back(s.substr(0, i));

18                 dfs(s.substr(i, s.size()-i), tmp, res, unused, dict);

19                 tmp.pop_back();

20             }

21         }

22         if (res.size() == pre) unused.insert(s);

23     }

24     vector<string> wordBreak(string s, unordered_set<string> &dict) {

25         vector<string> res;

26         unordered_set<string> unused;

27         vector<string> tmp;

28         dfs(s, tmp, res, unused, dict);

29         return res;

30     }

31 };

 C#

 1 public class Solution {

 2     public List<string> WordBreak(string s, ISet<string> wordDict) {

 3         List<string> ans = new List<string>();

 4         HashSet<string> unused = new HashSet<string>();

 5         List<string> tmp = new List<string>();

 6         dfs(s, ref tmp, ref ans, ref unused, wordDict);

 7         return ans;

 8     }

 9     public void dfs(string s, ref List<string> tmp, ref List<string> ans, ref HashSet<string> unused, ISet<string> wordDict) {

10         if (s.Length == 0) {

11             string res = "";

12             for (int i = 0; i < tmp.Count; i++) {

13                 if (i == 0) res += tmp[i];

14                 else res += " " + tmp[i];

15             }

16             ans.Add(res);

17             return;

18         }

19         if (unused.Contains(s) == true) return;

20         int pre = ans.Count;

21         for (int i = 1; i <= s.Length; i++) {

22             if (wordDict.Contains(s.Substring(0, i))) {

23                 tmp.Add(s.Substring(0, i));

24                 dfs(s.Substring(i, s.Length-i), ref tmp, ref ans, ref unused, wordDict);

25                 tmp.RemoveAt(tmp.Count-1);

26             }

27         }

28         if (ans.Count == pre) unused.Add(s);

29     }

30 }

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