Mex value

#include <bits/stdc++.h>
#define SZ(x) ((int) (x).size())
using namespace std;

typedef long long int64;

const int NMAX = 100000;

int arr[NMAX], frequency[NMAX + 1];

void Normalize(int v[], int n) {
    static int sortedArray[NMAX];
    memcpy(sortedArray, v, 4 * n);
    sort(sortedArray, sortedArray + n);
    
    int numUnique = unique(sortedArray, sortedArray + n) - sortedArray;
    for (int i = 0; i < n; i++) {
        v[i] = lower_bound(sortedArray, sortedArray + numUnique, v[i]) - sortedArray;
    }
}

int main(void) {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    
    int n, k; cin >> n >> k;
    for (int i = 0; i < n; i++) {
        cin >> arr[i];
    }
    Normalize(arr, n);
    
    for (int i = 0; i < n; i++) {
        frequency[arr[i]]++;
        if (i + 1 >= k) {
            int answer = 0;
            while (frequency[answer]) {
                answer++;
            }
            cout << answer << ' ';
            frequency[arr[i - k + 1]]--;
        }
    }
    cout << '\n';
    return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 1

Verdict: ACCEPTED

Test 7

Group: 1

Verdict: ACCEPTED

Test 8

Group: 1

Verdict: ACCEPTED

Test 9

Group: 1

Verdict: ACCEPTED

Test 10

Group: 1

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED

Test 15

Group: 2

Verdict: ACCEPTED

Test 16

Group: 2

Verdict: ACCEPTED

Test 17

Group: 2

Verdict: ACCEPTED

Test 18

Group: 2

Verdict: ACCEPTED

Test 19

Group: 2

Verdict: ACCEPTED

Test 20

Group: 2

Verdict: ACCEPTED