View Compilation Error

0_0_18227773_20663.cpp: In function 'void init()':
0_0_18227773_20663.cpp:17:24: error: 'memset' was not declared in this scope
  memset(f, -1, sizeof f);
                        ^
0_0_18227773_20663.cpp: In function 'int spfa(int, int)':
0_0_18227773_20663.cpp:37:33: error: 'memset' was not declared in this scope
  memset(flag, false, sizeof flag);
                                 ^