View Compilation Error

0_0_13145177_27397.cpp: In function 'void addnum(char*)':
0_0_13145177_27397.cpp:11:18: error: 'strlen' was not declared in this scope
  int len=strlen(s);
                  ^
0_0_13145177_27397.cpp: In function 'int main()':
0_0_13145177_27397.cpp:30:27: error: 'memset' was not declared in this scope
   memset(ans,0,sizeof(ans));
                           ^