链表的插入和删除操作

牛客：【模版】链表
笔记：如果结构体初始化不用传值就用new 结构体类型，如new LinkNode。如果有一个LinkNode类型的指针temp，要释放空间，就用delete temp。

#include <bits/stdc++.h>
using namespace std;

struct LinkNode {
	int value;
	LinkNode *next;
	LinkNode() {

	}
	LinkNode(int val, LinkNode *ln): value(val), next(ln) {

	}
};
int q;
LinkNode *head = new LinkNode(0, NULL);

LinkNode *query(int x) {
	LinkNode *t = head;
	while (t->next != NULL) {
		if (t->next->value == x) {
			return t;
		}
		t = t->next;
	}
	return t;
}

int main() {

	cin >> q;
	while (q--) {
		string op;
		int x, y;
		cin >> op;
		if (op == "insert") {
			cin >> x >> y;
			LinkNode *t, *nn = new LinkNode(y, NULL), *nt = new LinkNode;
			t = query(x);
			if (t->next) {
				nn->next = t->next;
				t->next = nn;
				
			} else
				t->next = nn;

		} else {
			cin >> x;
			LinkNode *t = query(x), *temp;
			if (t->next) {
				temp = t->next;
				t->next = t->next->next;
				delete temp;
			}
		}
	}
	LinkNode *t = head->next;
	if (t == NULL)
		cout << "NULL";
	while (t) {
		cout << t->value << " ";
		t = t->next;
	}
	return 0;
}