foo.cc: In function 'int main()':
foo.cc:13:6: error: overloaded function with no contextual type information
  max=0;
      ^
foo.cc:21:10: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   if(a[i]=a[min]||a[i]<0)
      ~~~~^~~~~~~~~~~~~~~
foo.cc:29:10: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   if(a[i]=a[min1]||a[i]>0)
      ~~~~^~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。