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
#include <algorithm>
#include <cassert>
#include <cstdio>
#include <limits>
#include <vector>

int distance[400][400];

const int MAX = 1000;

struct Route {
	int i, j;
	int distance;

	bool operator<(const Route& r) const {
		return distance > r.distance;
	}
};

int main() {
	std::vector<Route> routes;

	int T; scanf("%d\n", &T);
	while (T-- > 0) {
		int N; scanf("%d\n", &N);

		for (int i=0; i<N; ++i) {
			for (int j=0; j<N; ++j) {
				char c = getchar();
				if (i == j) {
					distance[i][j] = 0;
				} else if (c == '1') {
					distance[i][j] = 1;
				} else {
					distance[i][j] = MAX;
				}
			}
			assert(getchar() == '\n');
		}

		for (int k=0; k<N; ++k) {
			for (int i=0; i<N; ++i) {
				for (int j=0; j<N; ++j) {
					distance[i][j] = std::min(distance[i][j], distance[i][k] + distance[k][j]);
				}
			}
		}

		routes.clear();
		routes.reserve(N * N);
		for (int j=0; j<N; ++j) {
			for (int i=0; i<j; ++i) {
				if (distance[i][j] > 1) {
					routes.push_back({i, j, distance[i][j]});
				}
			}
		}
		std::sort(routes.begin(), routes.end());

		int best_result = MAX;
		for (int jT=0; jT<N; ++jT) {
			for (int iT=0; iT<jT; ++iT) {
				int max_dist = 1;
				for (const Route& route : routes) {
					if (distance[route.i][route.j] <= max_dist) {
						break;
					}
					int dist = std::min(
						distance[route.i][route.j],
						std::min(
							distance[route.i][iT] + distance[jT][route.j],
							distance[route.i][jT] + distance[iT][route.j]
						)
					);
					max_dist = std::max(max_dist, dist);
				}
				best_result = std::min(best_result, max_dist);
			}
			if (best_result == 1) {
				break;
			}
		}

		printf("%d\n", best_result);
	}
}