Problem link : https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=&problem=1594&mosmsg=Submission+received+with+ID+17149522
Solution :
#include<bits/stdc++.h>
#define pii pair<int,int>
using namespace std;
int cell[1050][1050];
int r,c;
int visited[1050][1050];
int fx[]= {1,-1,0,0};
int fy[]= {0,0,1,-1};
void bfs(pii s,pii d)
{
int b,i,k,x,y;
memset(visited,-1,sizeof(visited));
queue<pii>q;
pii a,u;
q.push(s);
visited[s.first][s.second]=0;
while(!q.empty())
{
a=q.front();
q.pop();
for(i=0; i<4; i++)
{
x=a.first+fx[i];
y=a.second+fy[i];
if(x>=0 and x<r and y>=0 and y<c and cell[x][y]!=-1 and visited[x][y]==-1)
{
visited[x][y]=visited[a.first][a.second]+1;
u=make_pair(x,y);
q.push(u);
}
if(a.first==d.first&&a.second==d.second) break;
}
}
cout<< visited[d.first][d.second]-visited[s.first][s.second]<<endl ;
}
int main()
{
int a,b,e,f,g,i,j,w;
while(cin>>r>>c && (r && c))
{
memset(cell,0,sizeof(cell));
scanf("%d",&a);
for(i=0; i<a; i++)
{
scanf("%d%d",&b,&w);
for(j=0; j<w; j++)
{
scanf("%d",&e);
cell[b][e]=-1;
}
}
pii s,d;
scanf("%d%d",&s.first,&s.second);
scanf("%d%d",&d.first,&d.second);
bfs(s,d);
}
}
