foo.cc: In function 'void st(int*, int, int*, int, int)':
foo.cc:9:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<a[v].size();j++)
               ~^~~~~~~~~~~~
foo.cc:18:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<a[v].size();j++)
               ~^~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:38:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[0].size();i++) cout<<a[0][i]<<" ";
              ~^~~~~~~~~~~~
foo.cc:40:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[1].size();i++) cout<<a[1][i]<<" ";
              ~^~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务