View Compilation Error

0_0_17439309_11559.cpp: In function 'void get_in()':
0_0_17439309_11559.cpp:23:32: error: 'memset' was not declared in this scope
     memset(head,-1,sizeof(head));en=0;  
                                ^
0_0_17439309_11559.cpp: In function 'void get_dy()':
0_0_17439309_11559.cpp:67:31: error: 'memset' was not declared in this scope
     memset(mark,0,sizeof(mark));  
                               ^
0_0_17439309_11559.cpp: In function 'void answer()':
0_0_17439309_11559.cpp:120:31: error: 'memset' was not declared in this scope
     memset(mark,0,sizeof(mark));  
                               ^