View Compilation Error

0_0_19468115_23448.cpp: In member function 'int ST::query(int, int)':
0_0_19468115_23448.cpp:26:26: error: 'swap' was not declared in this scope
         if(a > b)swap(a,b);
                          ^
0_0_19468115_23448.cpp: In function 'void init()':
0_0_19468115_23448.cpp:46:32: error: 'memset' was not declared in this scope
     memset(head,-1,sizeof(head));
                                ^
0_0_19468115_23448.cpp: In function 'int main()':
0_0_19468115_23448.cpp:84:18: error: 'scanf' was not declared in this scope
     scanf("%d",&T);
                  ^
0_0_19468115_23448.cpp:89:39: error: 'memset' was not declared in this scope
         memset(flag,false,sizeof(flag));
                                       ^
0_0_19468115_23448.cpp:106:37: error: 'printf' was not declared in this scope
         printf("%d\n",query_lca(u,v));
                                     ^