View Compilation Error

0_0_33976663_19405.cpp: In function 'int main()':
0_0_33976663_19405.cpp:16:15: error: 'strlen' was not declared in this scope
   n = strlen(s) ;
               ^
0_0_33976663_19405.cpp:21:31: error: 'memset' was not declared in this scope
   memset(cnt , 0 , sizeof(cnt)) ;
                               ^