/in/foo.cc:4:1: error: 'vector' does not name a type
 vector <int> a[100005];
 ^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:13:8: error: 'a' was not declared in this scope
   cin>>a[i]>>b[i];
        ^
/in/foo.cc:19:6: error: 'a' was not declared in this scope
   if(a[i].size()==2)
      ^