题解 | #牛的品种排序IV#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     *///black 0 white 1
    ListNode* sortCowsIV(ListNode* head) {
        // write code here
        ListNode* wp = new ListNode(1);
        ListNode* bp = new ListNode(0);
        ListNode* black = bp;
        ListNode* white = wp;
        while(head)
        {
		    //报错写法
            // if(node->val==0)
            // {
            //     black->val = 0;
            //     black = black->next;
            // }
            // if(node->val==1)
            // {
            //     white->val = 1;
            //     white = white->next;
            // }
            if(head->val==0)
            {
                black->next = head;
                black = black->next;
            }
            else
            {
                white->next = head;
                white = white->next;
            }
            head = head->next;
        }
        white->next = NULL;
        black->next = wp->next;
        return bp->next;
    }
};