输出链表中倒数第k个节点

输入一个单向链表，输出该链表中倒数第k个节点。

/*
* Copyright (c) 2011 alexingcool. All Rights Reserved.
*/
#include <iostream>

using namespace std;

int array[] = {5, 7, 6, 9, 11, 10, 8};
const int size = sizeof array / sizeof *array;

struct Node
{
Node(int i = 0, Node *n = NULL) : item(i), next(n) {}

int item;
Node *next;
};

Node* construct(int (&array)[size])
{
Node dummy;
Node *head = &dummy;

for(int i = 0; i < size; i++) {
Node *temp = new Node(array[i]);
head->next = temp;
head = temp;
}

return dummy.next;
}

void print(Node *head)
{
while(head) {
cout << head->item << " ";
head = head->next;
}
}

Node* findKnode(Node *head, int k)
{
Node *pKnode = head;

if(head == NULL) {
cout << "link is null" << endl;
return NULL;
}

while(k--) {
if(head == NULL) {
cout << "k is bigger than the length of the link" << endl;
return NULL;
}

head = head->next;
}

while(head) {
head = head->next;
pKnode = pKnode->next;
}

return pKnode;
}

void main()
{
Node *head = construct(array);
cout << "source link: ";
print(head);
cout << endl;
Node *kNode = findKnode(head, 5);
if(kNode != NULL)
cout << "the knode is: " << kNode->item << endl;
}

测试用例：

1. NULL Link

head = NULL;

2. normal Link, with normal k

k <= len(head);

3. normal Link, with invalid k

k > len(head)