foo.cc: In function 'int dfs(int, int, result)':
foo.cc:23:3: error: 'itoa' was not declared in this scope
   23 |   itoa(now_state, str, 10);
      |   ^~~~
foo.cc:25:16: error: 'strlen' was not declared in this scope
   25 |   for (int j = strlen(str) - 1; j >= 0; j--) {
      |                ^~~~~~
foo.cc:6:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    5 | #include <cstdlib>
  +++ |+#include <cstring>
    6 | using namespace std;
foo.cc:21:7: warning: unused variable 'tmp' [-Wunused-variable]
   21 |   int tmp = now_state;
      |       ^~~
foo.cc: In function 'int main()':
foo.cc:50:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   50 |   scanf("%d", &tmp);
      |   ~~~~~^~~~~~~~~~~~

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