题目：

题解：

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