https://www.luogu.com.cn/problem/CF706D

const int N = 3e6 + 10;
int trie[N][2], vis[N], idx;

void insert(int x)
{
    int p = 0;
    for (int i = 31; i >= 0; i--)
    {
        int u = (x >> i) & 1;
        if (!trie[p][u]) trie[p][u] = ++idx;
        p = trie[p][u];
        vis[p]++;//步骤
    }
}
void remove(int x)
{
    int p = 0;
    for (int i = 31; i >= 0; i--)
    {
        int u = (x >> i) & 1;
        p = trie[p][u];
        vis[p]--;//步骤
    }
}

ll find(int x)
{
    int p = 0;
    ll ans = 0;
    for (int i = 31; i >= 0; i--)
    {
        int u = (x >> i) & 1;
        if (trie[p][!u] && vis[trie[p][!u]]) ans = ans * 2 + 1, p = trie[p][!u];//步骤
        else  ans = ans * 2, p = trie[p][u];
    }
    return ans;
}

void solve()
{
    int n;
    cin >> n;
    insert(0);
    while (n--)
    {
        char c;
        int x;
        cin >> c >> x;
        if (c == '+') insert(x);
        else if (c == '-') remove(x);
        else cout << find(x) << '\n';
    }
}
int main()
{
    ios::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
    int t = 1;
    //cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}