Codeforces Round #534 (Div. 2) B. Game with string(stack具有纪念意义的一题)

#include <bits/stdc++.h>
using namespace std;
int pre[100005];

int main()
{
  string str;
  cin>>str;
  int len = str.length();
  stack<char> s;
  int ans = 0;
  for(int i=0;i<len;i++){
    if(s.size() == 0){s.push(str[i]);continue;}
    if(s.top() == str[i]){
      s.pop();
      ans++;
    }
    else{
      s.push(str[i]);
    }
  }
  if(ans % 2 == 1)puts("Yes");
  else puts("No");
  return 0;
}