View Code of Problem 3876

    #include<bits/stdc++.h>
    using namespace std;

    typedef long long ll;

    const int MAX = 5e6 + 100;
    const ll INF = 1e18;

    int n,q;
    int mp[MAX];

    int main()
    {
        scanf("%d%d",&n,&q);
        memset(mp,0,sizeof(mp));
        while(q--){
            char op[10];
            int x;
            scanf("%s%d",op,&x);
            if(op[0]=='C'){
                //mp[x]=!mp[x];
                if(mp[x]==0)    mp[x]=1;
                else mp[x]=0;
            }
            else{
                if(mp[x]==0){
                    printf("Yes\n");
                }
                else{
                    printf("No\n");
                }
            }
        }
        return 0;
    }