View Compilation Error

0_0_21978412_14660.cpp: In function 'int main()':
0_0_21978412_14660.cpp:18:37: error: 'memset' was not declared in this scope
   memset(a, 0, sizeof(int) * 5 * 101); //归零
                                     ^
0_0_21978412_14660.cpp:35:57: error: 'strcmp' was not declared in this scope
      if (strcmp(stu[a[i][k - 1]].time, stu[a[i][k]].time) > 0)  //按照时间大小降序排列
                                                         ^