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
58
59
60
61
62
63
64
65
66
67
#include <cstdio>
#include <cstdlib>
#include <cassert>

#include <algorithm>

int mat[512][512];

int single_case() {
    int n;
    char line[512];
    scanf("%d\n", &n);

    for (int i = 0; i < n; i++) {
        scanf("%s\n", line);
        for (int j = 0; j < n; j++) {
            mat[i][j] = (line[j] == '1') ? 1 : (n + 1);
        }
        mat[i][i] = 0;
    }

    // Floyd-Warshall (O(N^3))
    for (int k = 0; k < n; k++) {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                mat[i][j] = std::min(mat[i][j], mat[i][k] + mat[k][j]);
            }
        }
    }

    // for (int i = 0; i < n; i++) {
    //     for (int j = 0; j < n; j++) {
    //         printf("%d ", mat[i][j]);
    //     }
    //     puts("");
    // }

    // For each pair of cities, try to put a teleport there and find the worst case (O(N^4))
    int bestest = n + 1;
    for (int x = 0; x < n - 1; x++) {
        for (int y = x + 1; y < n; y++) {
            int worst = 0;
            for (int i = 0; i < n - 1; i++) {
                for (int j = i + 1; j < n; j++) {
                    // printf(" (%d %d): (%d, %d + %d | %d + %d)\n", i, j, mat[i][j], mat[i][x], mat[y][j],  mat[i][y], mat[x][j]);
                    worst = std::max(worst, std::min(mat[i][j], std::min(mat[i][x] + mat[y][j], mat[i][y] + mat[x][j])));
                }
            }
            // printf("Score for (%d, %d): %d\n", x, y, worst);
            bestest = std::min(bestest, worst);
        }
    }

    return bestest;
}

int main() {
    int t;
    scanf("%d\n", &t);

    while (t --> 0) {
        const int answer = single_case();
        printf("%d\n", answer);
    }

    return 0;
}