Leetcode:Word Break 字符串分解为单词

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) {
        std::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) {
                std::string str = s.substr(j, i - j);
                if (dp.at(j) == true && dict.find(str) != dict.end()) {
                    dp.at(i) = true;
                }
            }
        }
        return dp.at(s.size());
    }
};

Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word.

Return all such possible sentences.

For example, given
s = "catsanddog",
dict = ["cat", "cats", "and", "sand", "dog"].

A solution is ["cats and dog", "cat sand dog"].