foo.cc: In function 'int cal(int)':
foo.cc:32:2: error: 'vector' was not declared in this scope
   32 |  vector<int> a;
      |  ^~~~~~
foo.cc:5:1: note: 'std::vector' is defined in header '<vector>'; did you forget to '#include <vector>'?
    4 | #include <unordered_map>
  +++ |+#include <vector>
    5 | using namespace std;
foo.cc:32:9: error: expected primary-expression before 'int'
   32 |  vector<int> a;
      |         ^~~
foo.cc:33:11: error: 'a' was not declared in this scope
   33 |  while(x) a.push_back(x % 10), x /= 10, n ++;
      |           ^
foo.cc:34:7: error: 'a' was not declared in this scope
   34 |  sort(a.begin(), a.end());
      |       ^

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