아기 상어 2

#include <iostream> #include <vector> #include <queue> int N, M, _max; std::vector<std::vector<int> > map; std::vector<std::vector<int> > visited; std::vector<std::pair<int, int> > dir = {{-1, -1},{-1, 0},{-1, 1},{0, -1},{0, 1},{1, -1},{1, 0},{1, 1}}; std::queue<std::pair<int, int> > que; void output() { std::cout << _max; } int bfs(int i, int j) { que.push({i, j}); visited[i][j] = 1; while(!que.empty()) { auto front = que.front(); que.pop(); if (map[front.first][front.second] == 1) return visited[front.first][front.second] - 1; for(auto& d : dir) { if(front.first + d.first < 0 || front.first + d.first >= N || front.second + d.second < 0 || front.second + d.second >= M || visited[front.first + d.first][front.second + d.second]) continue; que.push({front.first + d.first, front.second + d.second}); visited[front.first + d.first][front.second + d.second] = visited[front.first][front.second] + 1; } } return 0; } void solution() { for(auto i = 0 ; i < N ; ++i) for(auto j = 0 ; j < M ; ++j) { visited = std::vector(N, std::vector(M, 0)); que = std::queue<std::pair<int, int> >(); _max = std::max(_max, bfs(i, j)); } } void input() { std::cin >> N >> M; map = std::vector(N, std::vector(M, 0)); for(auto& i : map) for(auto& j : i) std::cin >> j; } void preset() { std::ios_base::sync_with_stdio(false); std::cin.tie(NULL); std::cout.tie(NULL); } int main() { preset(); input(); solution(); output(); }