一:题目

二:上码

1:方法一：(虚拟一个首结点)

class Solution {
public:ListNode* removeElements(ListNode* head, int val) {//1.虚拟一个头结点  这样就不用单独处理了ListNode * virtuals = new ListNode(0);//给其开辟个空间并且赋初值virtuals->next = head;ListNode *node = virtuals;//这里的定义一个node是为了保持while(node != NULL && node->next != NULL){if(node->next->val == val){ListNode *temp = node->next;node->next = node->next->next;delete temp;}else{node = node->next;}}head = virtuals->next;//真正的头结点是虚拟结点的下一位//释放虚拟空间delete(virtuals);return head;}
};

2:方法二(不对首结点进行处理)

class Solution {
public:ListNode* removeElements(ListNode* head, int val) {//处理当删除的值为头节点的时候while(head != NULL && head->val == val){ListNode *node = head;head = node->next;delete node;}//处理头结点后面的结点ListNode* node = head;while(node != NULL && node->next != NULL){if(node->next->val == val) {ListNode *temp = node->next;node->next = node->next->next; delete temp;}else{node = node->next;}}return head;}
};