class Solution {
public:
    bool buddyStrings(string A, string B) {
        vector<int> a;
        if(A.length()==0 || B.length()==0) return false;
        else if(A.length()!=B.length()) return false;
        for(int i=0;i<A.length()&&i<B.length();i++){
            if(A[i]!=B[i]){
                a.push_back(i);
                }
        }
        char temp;
        if(A!=B){
            temp = A[a[0]];
            A[a[0]] = A[a[1]];
            A[a[1]] = temp;
            if(A==B) return true;
            else return false;
        }
        else {
            int i = 1;
            bool flag = true;
            while(i<A.length()){
                if(A[i] == A[0]) {flag = true; break;}
                else{
                    flag = false;
                }
                i++;
            }
            if(flag == true) return true;
            else return false;
        }
        return false;
    } 
};