单词拆分

    bool wordBreak(string s, vector<string>& wordDict) {
        std::unordered_set<std::string> wordSet;
        for(auto& it : wordDict) {
            wordSet.insert(it);
        }
        int sz = s.size();
        std::vector<bool> dp(sz + 1, false);
        dp[0] = true;
        for (int i = 1; i <= sz; ++i) {
            for (int j = 0; j < i; ++j) {
                if(dp[j] && wordSet.find(s.substr(j, i - j)) != wordSet.end()) {
                    dp[i] = true;
                    break;
                }
            }
        }
        return dp[sz];
    }