unsolved problem

class Solution {
public:
    bool repeatedSubstringPattern(string s) {
        int n =s.size();
        int i=1;
        
        while(s[0]!=s[i]&&i<n) i++;
        int sum =i;
        if(n/2<i) return false;
        int j=0;
        while(i<2*sum){
        if(s[j]==s[i])
        {i++;j++;}
            else 
            {return false ;}
        }
        return true;
    }
};