Yet Another MEX Problem

    1#include <bits/stdc++.h>
    2using namespace std;
    3typedef long long ll;
    4const long long INF = 1e17; //❄️
    5#define int long long
    6void solve() {
    7    int n, k; cin >> n >> k;
    8    vector<int> v(n);
    9    for (int i = 0; i < n; i++) cin >> v[i];
    10    vector<int> seen(n + 2); // mex is at most n + 1;
    11    for (int i = 0; i < v.size(); i++) {
    12        if (0 <= v[i] && v[i] <= n + 1) {
    13            seen[v[i]] = 1;
    14        }
    15    }
    16    int mex = 0;
    17    while (seen[mex]) mex++;
    18    cout << min(mex, k - 1) << '\n';
    19}
    20signed main() {
    21    ios::sync_with_stdio(0); cin.tie(0); 
    22    int t; cin >> t;
    23    while (t--) {
    24        solve();
    25    }
    26    return 0;
    27}