View Compilation Error

0_0_30460957_28641.cpp: In function 'void init()':
0_0_30460957_28641.cpp:20:32: error: 'memset' was not declared in this scope
     memset(head,-1,sizeof(head));
                                ^
0_0_30460957_28641.cpp: In function 'int Twosat(int)':
0_0_30460957_28641.cpp:41:29: error: 'memset' was not declared in this scope
     memset(vis,0,sizeof(vis));
                             ^