foo.cc: In function 'int isLeap(int)':
foo.cc:5:11: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(y%4==0&&y%100!=0||y%400==0)
     ~~~~~~^~~~~~~~~~
foo.cc: In function 'int monthday(int, int)':
foo.cc:19:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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