View Compilation Error

0_0_17045574_15250.cpp: In function 'int main()':
0_0_17045574_15250.cpp:44:33: error: 'memset' was not declared in this scope
         memset(res,0,sizeof(res));
                                 ^
0_0_17045574_15250.cpp:55:30: error: 'strlen' was not declared in this scope
             len=(int)strlen(s);
                              ^