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
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
#include <cstdio>
#include <vector>
#include <queue>
#include <algorithm>

int results[30];

int dists[407][407];

void bfs(int u, int n, std::vector<std::vector<int>>& v)
{
    std::vector<bool> visited(n, false);
    std::queue<int> q;

    for(int i=0; i<n; i++)
    {
        dists[u][i]=n+1;
    }
    dists[u][u]=0;

    q.push(u);
    while(!q.empty())
    {
        int w = q.front();
        q.pop();
        if(visited[w]) continue;
        visited[w]=true;
        for(int i=0; i<v[w].size(); i++)
        {
            q.push(v[w][i]);
            dists[u][v[w][i]] = std::min(dists[u][v[w][i]], dists[u][w]+1);
        }
    }
}

int main()
{
    int t,n;
    char c;
    scanf("%d", &t);
    for(int h=0; h<t; h++)
    {
        scanf("%d\n", &n);
        std::vector<std::vector<int>> v(n);
        for(int i=0; i<n; i++)
        {
            for(int j=0; j<n; j++)
            {
                scanf("%c", &c);
                if(c=='1')
                {
                    v[i].push_back(j);
                }
            }
            scanf("%c", &c);
        }
        for(int i=0; i<n; i++)
        {
            bfs(i, n, v);
        }
        int globalMaxDist = n+1;
        for(int i=0; i<n; i++)
        {
            for(int j=i+1; j<n; j++)
            {
                int localMaxDist = 0;
                for(int k=0; k<n; k++)
                {
                    for(int l=k+1; l<n; l++)
                    {
                        int distance1 = dists[j][k] + dists[i][l];
                        int distance2 = dists[j][l] + dists[i][k];
                        int distance3= dists[k][l];
                        int optDist = std::min(distance1, std::min(distance2, distance3));
                        if(optDist > localMaxDist)
                        {
                            localMaxDist = optDist;
                            if(localMaxDist >= globalMaxDist) break;
                        }
                    }
                    if(localMaxDist >= globalMaxDist) break;
                }
                globalMaxDist = std::min(localMaxDist, globalMaxDist);
            }
        }
        results[h] = globalMaxDist;
    }
    for(int h=0; h<t; h++)
    {
        printf("%d\n", results[h]);
    }
    return 0;
}