Word Break II



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"].

class Solution {
public:
	vector<string> wordBreak(string s, unordered_set<string> &dict) {
		if(m.find(s)!=m.end())  return m[s];
		vector<string> sentences;
		for(size_t i=0;i<s.size();++i){
			string ts = s.substr(0,i+1);
			unordered_set<string>::iterator iter = dict.find(ts);
			if(iter!=dict.end()){//找到了此子串，那么递归
				if(s.size() == i+1){
					sentences.push_back(ts);
				}else{
					vector<string> postResult=wordBreak(s.substr(i+1,s.size()-i-1),dict);
					if(postResult.size()){//后半部分可以分词
						combineStr(ts,postResult,sentences);
					} 
				}
			}
		}
		m[s]=sentences;
		return sentences; 
	}

private:
	void combineStr(string ts,vector<string> &postResult,vector<string> &dest){
		for(size_t i=0;i<postResult.size();++i){
			dest.push_back(ts+" "+postResult[i]);
		}
	}
private:
	map<string,vector<string>> m;
};