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".

利用动态规划思想 bvec[i] 表示 从开头到第i个元素之间的字符串是否出现在词典

bool wordBreak(string s, unordered_set<string> &dict){    int len = s.size();    vector<bool> bvec(len + 1, false);    bvec[0] = true;        for(int i = 1;i < len + 1; ++ i)    {        for(int j = i - 1;j >= 0; --j)        {            if(bvec[j] && dict.find(s.substr(j, i - j)) != dict.end())            {                bvec[i] = true;                break;            }        }    }    return bvec[len];}