foo.cc: In function 'void Merge(int*, int, int*, int, int*)':
foo.cc:18:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   if(a[i]<b[j])
     ^

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