foo.cc: In function 'int main()':
foo.cc:8:2: error: 'memset' was not declared in this scope
    8 |  memset(a, true, sizeof(a));
      |  ^~~~~~
foo.cc:3:1: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    2 | #include<vector>
  +++ |+#include <cstring>
    3 | using namespace std;

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