leetcode[139]Word Break

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".

class Solution {

public:

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

        if(s.empty())return true;

        if(dict.empty()) return s.empty();

        vector<bool> dp(1+s.length(),false);

        dp[0]=true;

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

        {

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

            {

                dp[i]=dp[j]&&(dict.count(s.substr(j,i-j)));

                if(dp[i])break;

            }

        }

        return dp[s.length()];

    }

};