View Compilation Error

0_0_18012004_13613.cpp: In function 'int main()':
0_0_18012004_13613.cpp:16:19: error: 'strlen' was not declared in this scope
       len=strlen(s);
                   ^
0_0_18012004_13613.cpp:17:29: error: 'memset' was not declared in this scope
       memset(ct,0,sizeof(ct));
                             ^