foo.cc: In function 'void dfs(int)':
foo.cc:49:3: error: 'memset' was not declared in this scope
   memset(change, 0, sizeof(change));
   ^~~~~~
foo.cc:49:3: note: suggested alternative: 'wmemset'
   memset(change, 0, sizeof(change));
   ^~~~~~
   wmemset

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