View Compilation Error

0_0_33868367_22354.cpp: In function 'int main()':
0_0_33868367_22354.cpp:30:33: error: 'memset' was not declared in this scope
   memset(begin, 0, sizeof(begin));
                                 ^
0_0_33868367_22354.cpp:39:30: error: 'strlen' was not declared in this scope
    int eChar = str[strlen(str) - 1] - 'a' + 1;
                              ^