foo.cc: In function 'int main()':
foo.cc:8:12: warning: unused variable 'index' [-Wunused-variable]
  int a[50],index[50]; 
            ^~~~~
foo.cc: In function 'int M(int*, int)':
foo.cc:29:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   if(a[i]>a[imax])
   ^~
foo.cc:31:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
    return imax;
    ^~~~~~

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