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| #include <iostream>
#include <algorithm>
#include <memory.h>
#include <vector>
#include <queue>
using namespace std;
int N,M;
int map[50][50];
int map_cpy[50][50];
bool visit[50][50];
int ans = 987654321;
int dx[4] = {0,1,0,-1};
int dy[4] = {-1,0,1,0};
bool choice[2501];
vector<pair<int,int>> virus;
queue<pair<int,int>> q;
void BFS(){
int sec = 0;
while(!q.empty()){
int cur_x = q.front().second;
int cur_y = q.front().first;
q.pop();
int time = map_cpy[cur_y][cur_x]+1;
for(int i=0;i<4;i++){
int near_y = cur_y+dy[i];
int near_x = cur_x+dx[i];
if(0<=near_x && near_x<N && 0<=near_y && near_y<N){
if(map_cpy[near_y][near_x]==0&&!visit[near_y][near_x]){
map_cpy[near_y][near_x] = time;
sec = max(sec,time);
visit[near_y][near_x] = true;
q.push(make_pair(near_y,near_x));
}
else if(map_cpy[near_y][near_x]==2&&!visit[near_y][near_x]){
map_cpy[near_y][near_x] = time;
visit[near_y][near_x] = true;
q.push(make_pair(near_y,near_x));
}
}
}
}
for(int i=0;i<N;i++)
for(int j=0;j<N;j++) {
if (map_cpy[i][j]==0)
return ;
}
ans = min(ans,sec-2);
}
void choose_virus(int choosed, int cur){
if(choosed == M){
memcpy(map_cpy,map,sizeof(map_cpy));
memset(visit,false,sizeof(visit));
queue<pair<int,int>> temp;
swap(temp,q);
for(int i=0;i<virus.size();i++){
if(choice[i]){
q.push(make_pair(virus[i].first,virus[i].second));
visit[virus[i].first][virus[i].second] = true;
}
}
BFS();
return ;
}
for(int i=cur;i<virus.size();i++){
choice[i] = true;
choose_virus(choosed+1,i+1);
choice[i]=false;
}
}
int main(void){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin>>N>>M;
bool flag = true;
for(int i=0;i<N;i++)
for(int j=0;j<N;j++){
cin>>map[i][j];
if(map[i][j]==2)
virus.push_back(make_pair(i,j));
if(map[i][j]==0)
flag = false;
}
if(flag){
cout<<"0"<<endl;
return 0;
}
choose_virus(0,0);
if(ans<87654321)
cout<<ans<<endl;
else
cout<<"-1"<<endl;
}
|
