leetcode刷题笔记 328.奇偶链表【中等】

1、先确定节点个数，再按照要求调整节点顺序

ListNode* oddEvenList(ListNode* head) {
	ListNode* last = head;
	ListNode* cur = head;
	int nums = 1;
	ListNode* odds = head;
	int total = 0; 
	while (cur) {
		total++;
		cur = cur->next;
	}
	cur = head;
	while (total) {
		if (nums % 2 == 1 && nums != 1) {//odd
			last->next = cur->next;
			ListNode* oddsnext = odds->next;
			odds->next = cur;
			cur->next = oddsnext;
			odds = cur;
			cur = last->next;
		}
		else {
			last = cur;
			cur = cur->next;
		}
		nums++;
		total--;
	}
	return head;
}

2、分离奇偶节点，然后合并

ListNode* oddEvenList(ListNode* head) {
	if (head == NULL || head->next == NULL || head->next->next == NULL)//长度小于等于2不用调
		return head;
	ListNode* odd = head, * even = head->next, * evenf = head->next;
	ListNode* cur = head->next->next;
	while (cur) {
		odd->next = cur;
		odd = cur;
		cur = cur->next;
		if (cur) {
			even->next = cur;
			even = cur;
			cur = cur->next;
		}
	}
	even->next = NULL;
	odd->next = evenf;
	return head;
}