王道数据结构链表2-2.5

//就地逆置链表

note：采用类似于头插法，把头结点拿下来，然后原链表按顺序接到头结点之后。

两个指针*p和*r，p用来遍历，r用来记录p的后继，

#include
using namespace std;
typedef struct lnode {
	int data;
	struct lnode* next;
}lnode,*linklist;
int a[5] = { 1,2,3,4,5 };
int n = 5;
void buildlist(linklist& L) {
	L = (lnode*)malloc(sizeof(lnode));
	if (L == NULL)return;
	lnode* s, * r = L;
	for (int i = 0; i < n; i++) {
		s = (lnode*)malloc(sizeof(lnode));
		s->data = a[i];
		r->next = s;
		r = r->next;
	}
	r->next = NULL;
}
void disp(linklist L) {
	lnode* s = L->next;
	while (s) {
		cout << s->data << "  ";
		s = s->next;
	}
	cout << endl;
}
void reverse(linklist L) {
	lnode* p = L->next, * r;
	L->next = NULL;//头结点拿下来
	while (p) {
		r = p->next;
		p->next = L->next;
		L->next = p;
		p = r;
	}
}
int main()
{
	linklist L;
	buildlist(L);
	disp(L);
	reverse(L);
	disp(L);
	return 0;
}