c++ - 在单个链表中搜索特定值

Question

我正在尝试实现一个通用的单链表。到目前为止，我已正确完成所有操作，但我无法让我的搜索功能正常工作。它应该在输出中打印“yes”，但没有任何反应。

这是我的代码:

#ifndef LinkedList_hpp
#define LinkedList_hpp

#include <iostream>

template<class T>
struct Node {
    T data;
    Node<T>* next;
};

template<class T>
class SingleLinkedList {
private:
    Node<T>* head;
    Node<T>* tail;

public:
    SingleLinkedList() {
        head = nullptr;
        tail = nullptr;
    }

    void createNode(const T& theData) {
        Node<T>* temp = new Node<T>;
        temp->data = theData;
        temp->next = nullptr;
        if(head == nullptr) {
            head = temp;
            tail = temp;
            temp = nullptr;
        }
        else {
            tail->next = temp;
            tail = temp;
        }
    }

    void display() {
        Node<T>* temp = new Node<T>;
        temp = head;
        while(temp != nullptr) {
            std::cout << temp->data << "\t";
            temp = temp->next;
        }
    }

    void insert_start(const T& theData) {
        Node<T>* temp = new Node<T>;
        temp->data = theData;
        temp->next = head;
        head = temp;
    }

    void insert_position(int pos, const T& theData) {
        Node<T>* previous = new Node<T>;
        Node<T>* current = new Node<T>;
        Node<T>* temp = new Node<T>;
        current = head;
        for(int i  = 1; i < pos; i++) {
            previous = current;
            current = current->next;
        }
        temp->data = theData;
        previous->next = temp;
        temp->next = current;
    }

    void delete_first() {
        Node<T>* temp = new Node<T>;
        temp = head;
        head = head->next;
        delete temp;
    }

    void delete_last() {
        Node<T>* previous = new Node<T>;
        Node<T>* current = new Node<T>;
        current = head;
        while(current->next != nullptr) {
            previous = current;
            current = current->next;
        }
        tail = previous;
        previous->next = nullptr;
        delete current;
    }

    void delete_position(int pos) {
        Node<T>* previous = new Node<T>;
        Node<T>* current = new Node<T>;
        current = head;
        for(int i = 1; i < pos; i++) {
            previous = current;
            current = current->next;
        }
        previous->next = current->next;
    }

    bool search(Node<T>* head, int x) {
        struct Node<T>* current = head;  
        while (current != NULL) {
            if (current->data == x)
                return true;
            current = current->next;
        }
        return false;
    }
};

#endif /* LinkedList_hpp */

这是 main.cpp:

#include <iostream>
#include "LinkedList.hpp"


int main(int argc, const char * argv[]) {

    SingleLinkedList<int> obj;
    obj.createNode(2);
    obj.createNode(4);
    obj.createNode(6);
    obj.createNode(8);
    obj.createNode(10);
    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"---------------Displaying All nodes---------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"-----------------Inserting At End-----------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.createNode(55);
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"----------------Inserting At Start----------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.insert_start(50);
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"-------------Inserting At Particular--------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.insert_position(5,60);
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"----------------Deleting At Start-----------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.delete_first();
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"-----------------Deleing At End-------------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.delete_last();
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    std::cout<<"--------------Deleting At Particular--------------";
    std::cout<<"\n--------------------------------------------------\n";
    obj.delete_position(4);
    obj.display();

    std::cout<<"\n--------------------------------------------------\n";
    system("pause");

    Node<int>* head = NULL;
    obj.search(head, 8) ? printf("Yes") : printf("No");


    return 0;
}

您可以看到我搜索值 8，它应该打印 yes，因为 8 仍在链表中。

Answer 1

这是你的 search功能:

bool search(Node<T>* head, int x) {
    struct Node<T>* current = head;  
    while (current != NULL) {
        if (current->data == x)
            return true;
        current = current->next;
    }
    return false;
}

它使用参数 head作为第一个参数传入，而不是 SingleLinkedList<T>::head成员变量。

因为你调用它传递一个空指针作为第一个参数，你不会找到任何东西。

简单修复:从 search 中删除第一个参数功能:

bool search(T x) { ... }

如您所见，我还将您搜索的值的参数更改为模板类型。