题解 | #【模板】链表#

#include <iostream>
using namespace std;
struct list {
    int data;
    list* next;
};
void insert(list* p, int x, int y) {
    list* q = p;
    p = p->next;
    while (p != NULL) {
	  //插入操作放于循坏外，能够在x值不存在情况下把节点插入最后
        if (p->data == x)
        break;
        q = p;
        p = p->next;
    }
    list* t = new list();
    t->data = y;
    q->next = t;
    t->next = p;
}
void del(list* p, int x) {
    list* q = p;
    p = p->next;
    while (p != NULL) {
	  //如果将删除操作放在循环外，可能删除空列表，因而确定有x再执行删除操作
        if (p->data == x)
        {
        q->next = p->next;
        p->next = NULL;
        delete p;
        break;
        }
        q = p;
        p = p->next;
    }
    
}
int main() {
    int n;
    cin >> n;
    list* head = new list();
    head->next = NULL;
    while (n--) { // 注意 while 处理多个 case
        string s;
        int x, y;
        cin >> s;
        if (s == "insert") {
            cin >> x >> y;
            insert(head, x, y);
        }
        if (s == "delete") {
            cin >> x;
            del(head, x);
        }
    }
    list* t = head->next;
    if (t == NULL)
        cout << "NULL";
    else while (t != NULL) {
            cout << t->data << " ";
            t = t->next;
        }
}
// 64 位输出请用 printf("%lld")