/in/foo.cc: In function 'int main()':
/in/foo.cc:8:12: error: 'strlen' was not declared in this scope
  int len = strlen(ss);
            ^~~~~~
/in/foo.cc:8:12: note: suggested alternative: 'mbrlen'
  int len = strlen(ss);
            ^~~~~~
            mbrlen
/in/foo.cc:8:6: warning: unused variable 'len' [-Wunused-variable]
  int len = strlen(ss);
      ^~~
/in/foo.cc:11:6: warning: unused variable 'i' [-Wunused-variable]
  int i, n = 1;
      ^
/in/foo.cc:11:9: warning: unused variable 'n' [-Wunused-variable]
  int i, n = 1;
         ^
/in/foo.cc:12:6: warning: unused variable 'arr' [-Wunused-variable]
  int arr[100] ={0}, k = 0;
      ^~~
/in/foo.cc:12:21: warning: unused variable 'k' [-Wunused-variable]
  int arr[100] ={0}, k = 0;
                     ^