foo.cc: In function 'void dfs(int, int)':
foo.cc:12:14: error: 'b' was not declared in this scope
   if(a[x] == b[x]){
              ^
foo.cc:14:4: error: expected ';' before 'j'
    j=x+1;
    ^
foo.cc: In function 'int main()':
foo.cc:21:8: error: expected primary-expression before '%' token
  scanf(%d,n);
        ^
foo.cc:21:9: error: 'd' was not declared in this scope
  scanf(%d,n);
         ^
foo.cc:23:9: error: expected primary-expression before '%' token
   scanf(%d,b[i]);
         ^
foo.cc:23:12: error: 'b' was not declared in this scope
   scanf(%d,b[i]);
            ^
foo.cc:26:8: error: expected primary-expression before '%' token
  prinf(%d,ans);
        ^
foo.cc:26:2: error: 'prinf' was not declared in this scope
  prinf(%d,ans);
  ^~~~~
foo.cc:26:2: note: suggested alternative: 'printf'
  prinf(%d,ans);
  ^~~~~
  printf

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