手撕链表~~_js手撕链表

链表的创建以及实现增删改查功能，利用了哑节点把头节点“大众化”
 
//创建结构体
struct Node {
	int val;
	Node* next;
	Node(int val) {
		this->val = val;
		this->next = nullptr;
	}
};
//全局变量
Node* head;
Node* tail;
Node* dummyhead;
//用数组传参创建链表
Node* createList(vector<int>&a) {
	for (int i = 0; i < a.size(); i++) {
		Node *newnode = new Node(a[i]);
		if (!head) {
			head = newnode;
			tail = newnode;
		}
		else {
			tail->next = newnode;
			tail = newnode;
		}
	}
	return head;
}
//打印
void print(Node* head) {
	while (head) {
		cout << head->val<<" ";
		head = head->next;
	}
	printf("\n");
	return;
}
//增加：在index个节点前加节点val（index从0计数）
Node* add(int val,int index) {
	if (!head) return head;
	dummyhead = new Node(-1);
	Node* newnode = new Node(val);
	dummyhead->next = head;
	Node* cur = dummyhead;
	while (index) {
		cur = cur->next;
		index--;
	}
	newnode->next = cur->next;
	cur->next = newnode;
	return dummyhead->next;
}
//删除值为val的所有节点
Node* deleteNode(int val) {
	if (!head) return head;
	dummyhead = new Node(-1);
	dummyhead->next = head;
	Node* cur = dummyhead;
	while (cur->next) {
		if (cur->next->val==val) {
			cur->next = cur->next->next;
		}
		else {
			cur = cur->next;
		}
	}
	return dummyhead->next;
}
//改：将节点nums1改为nums2
Node* changeNode(int nums1, int nums2) {
	if (!head) return head;
	Node* p = head;
	while (p) {
		if (p->val == nums1) {
			p->val = nums2;
		}
		p = p->next;
	}
	return head;
}
//查找
bool get(int target) {
	if (!head) return head;
	dummyhead = new Node(-1);
	dummyhead->next = head;
	while (head) {
		if (head->val == target) {
			return 1;
		}
		head = head->next;
	}
	return 0;
}