View Compilation Error

0_0_19194771_14954.cpp: In function 'void Polish(char*, int)':
0_0_19194771_14954.cpp:28:34: error: 'memset' was not declared in this scope
  memset(output,'\0',sizeof output); //输出串
                                  ^
0_0_19194771_14954.cpp: In function 'int main()':
0_0_19194771_14954.cpp:139:29: error: 'strlen' was not declared in this scope
   Polish(input, strlen(input));
                             ^