844. Backspace String Compare

class Solution {
public:
    bool backspaceCompare(string S, string T) {
        string s = "", t="";
        for(int i=0;i<S.length();i++){
            if(S[i] == '#'){//注意是字符之间的比较，不能用字符和字符串进行比较-->错误ISO C forbids comparison between pointer and integer [-fpermissive]
                if(s.length()!=0)
                    s.pop_back();
            }
            else{
                s+=S[i];
            }
        }
        for(int i=0;i<T.length();i++){
            if(T[i] == '#'){
                if(t.length()!=0)
                    t.pop_back();
            }
            else{
                t+=T[i];
            }
        }
        return s==t;
    }
};