View Compilation Error

0_0_28995195_30037.cpp: In function 'int main()':
0_0_28995195_30037.cpp:165:13: error: 'graph' was not declared in this scope
         mem(graph, 0);
             ^
0_0_28995195_30037.cpp:32:26: note: in definition of macro 'mem'
 #define mem(a, b) memset(a, b, sizeof(a))
                          ^