連結串列反序，設有資料結構

typedef struct _list_node

{ double keyVal;

struct _list_node *next;

}ListNode;

ListNode* reverseList(ListNode* head)

{

ListNode *p1, *p2 , *p3;

//連結串列為空，或是單結點連結串列直接返回頭結點

if (head == NULL || head->next == NULL)

{

return head;

}

p1 = head;

p2 = head->next;

while (p2 != NULL)

{

p3 = p2->next;

p2->next = p1;

p1 = p2;

p2 = p3;

}

head->next = NULL;

head = p1;

return head;

}