[LeetCode] 430. Flatten a Multilevel Doubly Linked List 压平一个多层的双向链表
Youaregivenadoublylinkedlistwhichinadditiontothenextandpreviouspointers,itcouldhaveachildpointer,whichmayormaynotpointtoaseparatedoublylinkedlist.Thesechildlistsmayhaveoneormorechildrenoftheirown