word-break leetcoder C++

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".

C++

class Solution {
public:
    bool wordBreak(string s, unordered_set<string> &dict) {
        vector<bool> flag(s.length()+1,false);
        flag[0] = true;
        for(int i = 1; i < s.length() + 1; ++i){
            for (int j = i + 1; j >= 0; j--){
                if (flag[j] && dict.count(s.substr(j,i-j)) != 0){
                    flag[i] = true;
                    break;
                }
            }
        }
        return flag[s.length()];
    }
};