https://school.programmers.co.kr/learn/courses/30/lessons/12973
#include <iostream>
#include <string>
#include <stack>
using namespace std;
int solution(string s)
{
stack <char> stk;
int answer = -1;
int len = s.size();
stk.push(s[0]);
for(int i = 1; i<len; i++){
if(!stk.empty()&&stk.top() == s[i]){
stk.pop();
}
else{
stk.push(s[i]);
}
}
if(stk.empty()){
return 1;
}
else{
return 0;
}
return 1;
}