lintcode:Word Break

Given a string s and a dictionary of words dict, determine if s can be break into a space-separated sequence of one or more dictionary words.

设res[i]表示s的前i个数字母能否分拆后在dict中找到。

则

如果

，则res[i]=true;

class Solution {
public:
    /**
     * @param s: A string s
     * @param dict: A dictionary of words dict
     */
    bool wordBreak(string s, unordered_set<string> &dict) {
        // write your code here

        int len=s.size();

        if(len==0){
            return true;
        }

        if(dict.size()==0){
            return false;
        }

        int maxLen=0;
        for(string str:dict){
            if(str.size()>maxLen){
                maxLen=str.size();
            }
        }

        vector<bool> res(len+1,false);
        res[0]=true;

        for(int i=1;i<=len;i++){
            for(int j=i-1;j>=0;j--){

                if(i-j>maxLen){
                    break;
                }

                bool flag=res[j]&& dict.find(s.substr(j,i-j))!=dict.end();
                if(flag){
                    res[i]=true;
                    break;
                }
            }
        }

        return res[len];
    }
};