LeetCode-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"].

动归

class Solution {
public:
    void sub(vector<vector<int> >& str,string& s,int index,string& one, vector<string>& ret){
        if(index==0){
            ret.push_back(one);
        }
        else{
            int length=one.length();
            for(int i=0;i<str[index].size();i++){
                if(index==s.length()){
                    one=s.substr(str[index][i],index-str[index][i])+one;
                }
                else{
                    one=s.substr(str[index][i],index-str[index][i])+" "+one;
                }
                sub(str,s,str[index][i],one,ret);
                one=one.substr(one.length()-length,length);
            }
        }
    }
    vector<string> wordBreak(string s, unordered_set<string> &dict) {
        int maxLen=0;
        for(unordered_set<string>::iterator it=dict.begin();it!=dict.end();it++){
            if( (*it).length()>maxLen)maxLen=(*it).length();
        }
        string tmp;
        vector<vector<int> >str;
        vector<bool>acc;
        acc.resize(s.length()+1,false);
        str.resize(s.length()+1);
        acc[0]=true;
        int i=0;
        if(acc[i]){
            int top=min(maxLen,(int)s.length()-i);
            for(int j=1;j<=top;j++){
                tmp=s.substr(i,j);
                if(dict.find(tmp)!=dict.end()){
                    acc[i+j]=true;
                    str[i+j].push_back(0);
                }
            }
        }
        for(int i=1;i<s.length();i++){
            if(acc[i]){
                int top=min(maxLen,(int)s.length()-i);
                for(int j=1;j<=top;j++){
                    tmp=s.substr(i,j);
                    if(dict.find(tmp)!=dict.end()){
                        acc[i+j]=true;
                        str[i+j].push_back(i);
                    }
                }
            }
        }
        string one="";
        vector<string> ret;
        sub(str,s,s.length(),one,ret);
        return ret;
    }
};