【C语言】求带环单链表的环长

思想：快慢指针，先让快指针追上慢指针，再快指针不动，慢指针单步走，两个指针再次相遇时，慢指针在第一次相遇后所单步走的步数就为环长



[align=left]intLengthCycle(Plinklist*pplist)[/align]

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

[align=left] while(fast&&fast->next) [/align]

[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]
intcount
= 0;
[align=left] do[/align]
[align=left] {[/align]
[align=left] slow = slow->next;[/align]
[align=left] count++;[/align]
}while(fast
!= slow);
[align=left] returncount;[/align]

[align=left]}[/align]