View Compilation Error

0_0_26105538_23836.cpp: In function 'int main()':
0_0_26105538_23836.cpp:85:19: error: 'reverse' was not declared in this scope
   reverse(a, a + n);
                   ^
0_0_26105538_23836.cpp:111:25: error: 'memset' was not declared in this scope
   memset(a, 0, sizeof(a));
                         ^