1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
#include <cstdio>
#include <cstdlib>
#include <cassert>

#include <vector>

int main() {
    std::vector<int> day_diffs;
    std::vector<int> curr_tracks, prev_tracks;

    int k, n;
    scanf("%d %d", &k, &n);
    day_diffs.resize(k + 1, 0);
    curr_tracks.resize(n, 1);

    auto flush_tracks = [&] (const std::vector<int>& tracks, int day) {
        for (int track : tracks) {
            if (track > 0) {
                day_diffs[track]++;
                day_diffs[day]--;
            }
        }
    };

    for (int i = 2; i <= k; i++) {
        std::swap(curr_tracks, prev_tracks);
        scanf("%d", &n);
        curr_tracks.clear();
        curr_tracks.reserve(n);
        for (int j = 0; j < n; j++) {
            int x;
            scanf("%d", &x);
            if (x == 0) {
                curr_tracks.push_back(i);
            } else {
                int track_start = std::abs(prev_tracks[x - 1]);
                prev_tracks[x - 1] = -track_start;
                curr_tracks.push_back(track_start);
            }
        }
        flush_tracks(prev_tracks, i);
    }
    flush_tracks(curr_tracks, k + 1);

    int currcount = 0;
    int maxcount = 0;
    for (int i = 0; i <= k + 1; i++) {
        currcount += day_diffs[i];
        maxcount = std::max(maxcount, currcount);
    }

    assert(currcount == 0);

    printf("%d\n", maxcount);

    return 0;
}