[Leetcode] Word BreakII

Question:

Given a string s and a dictionary of
words dict, add spaces in s to construct a
sentence where each word is a valid dictionary word.

Return all such possible sentences.

For example,
given
s = "catsanddog",
dict = ["cat",
"cats", "and", "sand", "dog"].

A solution is ["cats and dog", "cat sand dog"].

----------------------------------------------

Solution:

dfs.

但是需要注意的是，在dfs之前，需要判断这个string能不能被这个dictionary分割（Word
Break）。

 1 public class Solution {

 2     public List<String> wordBreak(String s, Set<String> dict) {

 3         List<String> result=new ArrayList<String>();

 4         if(!wordBreakPossible(s,dict)) return result;

 5         dfs(s,dict,result,"",0);

 6         return result;

 7     }

 8

 9     private void dfs(String s, Set<String> dict, List<String> result,String temp, int start) {

10         // TODO Auto-generated method stub

11         if(start==s.length())

12             result.add(temp);

13         else{

14             if(start!=0)

15                 temp+=" ";

16             for(int i=start;i<s.length();i++){

17                 String word=s.substring(start, i+1);

18                 if(dict.contains(word))

19                     dfs(s,dict,result,temp+word,i+1);

20             }

21         }

22     }

23

24     private boolean wordBreakPossible(String s, Set<String> dict) {

25         // TODO Auto-generated method stub

26         boolean[] state=new boolean[s.length()+1];

27         state[0]=true;

28         for(int i=1;i<=s.length();i++){

29             for(int j=i-1;j>=0;j--){

30                 if(state[j]&&dict.contains(s.substring(j, i))){

31                     state[i]=true;

32                     break;

33                 }

34

35             }

36         }

37         return state[s.length()];

38     }

39 }