View Compilation Error

0_0_18787648_19928.cpp: In function 'void Polish(char*, int)':
0_0_18787648_19928.cpp:28:36: error: 'memset' was not declared in this scope
  memset(output, '\0', sizeof output);  //输出串  
                                    ^
0_0_18787648_19928.cpp: In function 'int main()':
0_0_18787648_19928.cpp:139:29: error: 'strlen' was not declared in this scope
   Polish(input, strlen(input));
                             ^