剑指offer---链表中倒数第k个结点

/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* FindKthToTail(ListNode* pListHead, unsigned int k)
{
if(!pListHead)
return NULL;

ListNode *p = pListHead;
unsigned int n = 0;
while(p)
{
p = p->next;
++n;
}
if(n < k)
return NULL;

p = pListHead;
unsigned int cnt = 0;
while(cnt < n-k && p)
{
p = p->next;
++cnt;
}

return p;
}
};