leetcode-139-Word Break

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Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

Note:

  • The same word in the dictionary may be reused multiple times in the segmentation.
  • You may assume the dictionary does not contain duplicate words.
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Example 1:

Input: s = "leetcode", wordDict = ["leet", "code"]
Output: true
Explanation: Return true because "leetcode" can be segmented as "leet code".
Example 2:

Input: s = "applepenapple", wordDict = ["apple", "pen"]
Output: true
Explanation: Return true because "applepenapple" can be segmented as "apple pen apple".
             Note that you are allowed to reuse a dictionary word.
Example 3:

Input: s = "catsandog", wordDict = ["cats", "dog", "sand", "and", "cat"]
Output: false
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bool wordBreak(string s, unordered_set<string> &dict) {
    if(dict.size()==0) return false;
    
    vector<bool> dp(s.size()+1,false);
    dp[0]=true;
    
    for(int i=1;i<=s.size();i++)
    {
        for(int j=i-1;j>=0;j--)
        {
            if(dp[j])
            {
                string word = s.substr(j,i-j);
                if(dict.find(word)!= dict.end())
                {
                    dp[i]=true;
                    break; //next i
                }
            }
        }
    }
    
    return dp[s.size()];
}
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