View Compilation Error

0_0_15033947_12885.cpp: In function 'bool BFS(int, int)':
0_0_15033947_12885.cpp:28:32: error: 'memset' was not declared in this scope
   memset(sign, -1, sizeof(sign));  
                                ^
0_0_15033947_12885.cpp: In function 'void init()':
0_0_15033947_12885.cpp:92:39: error: 'memset' was not declared in this scope
 void init(){memset(head,-1,sizeof head);edgenum = 0;}
                                       ^
0_0_15033947_12885.cpp: In function 'int main()':
0_0_15033947_12885.cpp:107:30: error: 'memset' was not declared in this scope
     memset(use, 0, sizeof use);
                              ^