【C语言】找带环单链表的环入口

[align=left]思想：（1）快慢指针，先让快指针追上慢指针[/align]
[align=left] （2）令快指针指向表头，慢指针的指向不变，两个指针同时开始走[/align]
[align=left] （3）两个指针相遇时，所指节点即为环的入口[/align]



[align=left]Node*FindEntry(Plinklist*pplist)[/align]

[align=left]{[/align]
[align=left] assert(pplist);[/align]
Node*fast
= *pplist;

Node*slow
= *pplist;
while(fast&&fast->next
) //让快指针追上慢指针

[align=left] {[/align]
[align=left] fast = fast->next->next;[/align]
[align=left] slow = slow->next;[/align]
if(fast
== slow)
[align=left] {[/align]
[align=left] break;[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] fast = *pplist;[/align]
while(fast
!= slow)
[align=left] {[/align]
[align=left] fast = fast->next;[/align]
[align=left] slow = slow->next;[/align]
[align=left] }[/align]
[align=left] returnfast;[/align]
[align=left]}[/align]