View Compilation Error

0_0_20671010_25068.cpp: In function 'bool isPrime(int)':
0_0_20671010_25068.cpp:8:23: error: 'sqrt' was not declared in this scope
     int mid = sqrt(num);
                       ^
0_0_20671010_25068.cpp: In function 'int main()':
0_0_20671010_25068.cpp:38:35: error: 'memset' was not declared in this scope
         memset(vis, 0, sizeof(vis));
                                   ^