1292A - NEKO's Maze Game - CodeForces Solution

#include <bits/stdc++.h>
#define fastio                    \
	ios_base::sync_with_stdio(0); \
	cin.tie(0);
#define vi vector<int>
#define vl vector<long long>
#define vc vector<char>
#define vs vector<string>
#define pi pair<int, int>
#define pl pair<ll, ll>
#define vp vector<pi>
#define vpl vector<pl>
#define ll long long
#define MAX 2147000000
#define MOD 1000000007
using namespace std;

int main(){
	fastio;
    int n, q;
    cin >> n >> q;
    set<int> A, B;
    int cnt{0};
    while(q--){
        int a, b;
        cin >> a >> b;
        if(a == 1){
            if(A.count(b)){
                for(int i{-1}; i <= 1; ++i){
                    if(B.count(b + i)) cnt--;
                }
                A.erase(b);
            }
            else{
                for(int i{-1}; i <= 1; ++i){
                    if(B.count(b + i)) cnt++;
                }
                A.insert(b);
            }
        }   
        else{
            if(B.count(b)){
                for(int i{-1}; i <= 1; ++i){
                    if(A.count(b + i)) cnt--;
                }
                B.erase(b);
            }
            else{
                for(int i{-1}; i <= 1; ++i){
                    if(A.count(b + i)) cnt++;
                }
                B.insert(b);
            }
        }
        if(!B.count(n) && cnt == 0) cout << "Yes\n";
        else cout << "No\n";
    }
}