View Compilation Error

0_0_36973777_16284.cpp: In function 'int main()':
0_0_36973777_16284.cpp:29:28: error: 'memset' was not declared in this scope
   memset(cnt, 0, sizeof cnt);
                            ^
0_0_36973777_16284.cpp:32:20: error: 'strlen' was not declared in this scope
   int n = strlen(mh);
                    ^