c++ - 如何从链表中删除节点？

Question

将整数添加到列表中工作正常，但删除和打印时出现问题。

我对调试器还不是很友好，但我发现节点指针“first”有错误。它的值为-17891602。我不知道发生了什么......

#include <iostream>
using namespace std;

class nodeList;

class node {
    friend class nodeList;
private:
    int data;
    node* link;
public:
    node() { //constructor
        data = 0;
        link = NULL;
    }
    node(int d) { //constructor
        data = d;
        link = NULL;
    }
    node(int d, node* l){ //constructor
        data = d;
        link = l;
    }
};

class nodeList {
private:
    node* first;
    int num = 0;
    node* nt;
public:
    nodeList() {
        first = new node();
    }
    node* end(node* t){ //return pointer of last element
        t = first;
        for (int i = 0; i < num; i++){
            t = t->link;
        }
        return t;
    }
    void add(int a){ //add 'a' at the end of the list
        node* x = new node(a);
        node* y = this->end(nt);
        y->link = x;
        num++;
    }

    void del(int n){ //n : data of element that you want to delete from list
        node* temp = first;
        node* pretemp = NULL;
        node* x;
        int i;
        for (i = 0; i <= this->num; i++){ //loop to find 'n'
            pretemp = temp;
            temp = temp->link;
            if (n == temp->data){
                break;
            }
        }
        temp = first;
        for (int j = 0; j<i; j++){ //i : where 'n' is,
            temp = temp->link;
        }
        x = temp->link;
        pretemp->link = x;
        delete temp;
        num--;
    }
    void printList(){
        node* temp = first;
        temp = temp->link;
        for (int i = 0; i<this->num; i++){
            cout << temp->data << endl;
            temp = temp->link;
        }
    }
};

int main(){
    nodeList *l = new nodeList();
    int a;
    int select;
    while (1){
        cout << "1. ADD  2. DELETE  3. PRINT" << endl;
        cin >> select;

        if (select == 1){
            cout << "Enter an integer: ";
            cin >> a;
            if (cin.fail()) {
                cout << "Wrong input" << endl;
                break;
            }
            l->add(a);
            l->printList();
        }

        if (select == 2){
            cout << "Enter the data of the element you want to delete: ";
            cin >> a;
            if (cin.fail()) {
                cout << "Wrong input" << endl;
                break;
            }
            l->del(a);
            l->printList();
        }

        if (select == 3){
            l->printList();
        }
    }
}

Answer 1

您的 del 函数删除临时节点(您需要删除的节点之前的节点)。

这是可能的解决方法:

//n : data of element that you want to delete from list
void del(int n)
{
    //loop to find 'n'
    for (node *tmp = first; tmp->link; tmp = tmp->link)
    {
        if (n == tmp->link->data)
        {
            node *x = tmp->link;
            tmp->link = tmp->link->link;
            delete x;
            num--;
            break;
        }
    }
}

此外，您的 del 是否应该删除所有具有 data == n 的节点？