139. Word Break Leetcode Java

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

For example, given
s = "leetcode",
dict = ["leet", "code"].

Return true because "leetcode" can be segmented as "leet code".

Solution:

Dynamic programming

The recursion equation is straightforward, for res[i], if there exist an index j between 0 and i can make res[j]&&dict.contains(s.substring(j,i)) true, then res[i] will be true. 

 public boolean wordBreak(String s, Set<String> dict) {  
     if(s==null) return false;  
     if(s.length()==0) return true;  
     boolean[] res=new boolean[s.length()+1];  
     res[0]=true;  
     for(int i=0;i<s.length();i++){  
       for(int j=0;j<=i;j++){  
         if(res[j] && dict.contains(s.substring(j,i+1))){  
           res[i+1]=true;  
           break;  
         }  
       }  
     }  
     return res[s.length()];  
   }