foo.cc: In function 'int main()':
foo.cc:11:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(a2>a1&&a1>a3||a3>a1&&a1>a2) b=a1;
     ~~~~~^~~~~~~
foo.cc:12:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(a1>a2&&a2>a3||a3>a2&&a2>a1) b=a2;
     ~~~~~^~~~~~~
foo.cc:13:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(a1>a3&&a3>a2||a2>a3&&a3>a1) b=a3;
     ~~~~~^~~~~~~
foo.cc:17:11: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<b<<" "<<max<<endl;
           ^~~
foo.cc:17:16: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<b<<" "<<max<<endl;
                ^~~

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