此链表实现中的错误

Question

I'm currently self-learning the Data Structures side of programming, which includes linked lists. I coded a C++ program that involves creating a list, inserting nodes, searching through the list for a value, outputting the list, and deleting them. For some reason, I'm getting the wrong output. Any kind of help or suggestions are greatly appreciated.

#include <iostream>
using namespace std;

typedef int DataItem;

struct Node {
    DataItem data;
    Node *next;
};

Node* ListSearch(DataItem value, Node *head) {
    if(head == NULL)
        return NULL;
    Node *nodePtr = head;
    while(nodePtr!= NULL){
        if (nodePtr->data == value)
            return nodePtr;
        nodePtr = nodePtr->next;
    }
    return NULL;
}

void InsertNewLast(DataItem value, Node **L) {
    Node *nodePtr = *L;
    if(nodePtr == NULL){
        nodePtr = new Node();
        nodePtr->data = value;
        nodePtr->next = NULL;
        *L = nodePtr;
    }
    else{
        while(nodePtr->next!= NULL){ //go through the list
            nodePtr = nodePtr->next;
        }
        nodePtr->next = new Node();
        nodePtr->data = value;
    }
    return;
}
void DeleteLastNode(Node **L) {
    Node* nodePtr = *L;
    if(nodePtr == NULL)
            return;
    if(nodePtr != NULL && nodePtr->next != NULL){
        Node *newLast = nodePtr;
        while(newLast->next->next != NULL){
            newLast = newLast->next;
        }
        delete newLast->next;
        newLast->next=NULL;
    }
    else{
        delete nodePtr;
        nodePtr = NULL;
    }
    *L = nodePtr;
}

void PrintList(Node *head) {
    Node* nodePtr = head;
    if(nodePtr== NULL)
        return;
    else{
        while(nodePtr!=NULL){
            cout << "[" << nodePtr->data << "]";
            nodePtr = nodePtr->next;
            if (nodePtr != NULL)
                cout << "->";
        }
    cout << endl;
    return;
    }
}

int main () { 
    Node *head;
    Node *nodePtr; 
    DataItem searchValue;
    head = NULL;

    // Printing and Inserting...
    PrintList(head);
    InsertNewLast(10, &head);
    PrintList(head);
    InsertNewLast(20, &head);
    PrintList(head);
    InsertNewLast(30, &head);
    PrintList(head);
    InsertNewLast(40, &head);
    PrintList(head);
    InsertNewLast(50, &head);
    PrintList(head);
    // Searching...
    searchValue = 10;
    nodePtr = ListSearch(searchValue, head);
    if (nodePtr != NULL) {
    cout << "Search value " << searchValue << " was FOUND" << endl;
    } else {
    cout << "Search value " << searchValue << " was NOT FOUND" << endl;
    }
    searchValue = 5;
    nodePtr = ListSearch(searchValue, head);
    if (nodePtr != NULL) {
    cout << "Search value " << searchValue << " was FOUND\n";
    } else {
    cout << "Search value " << searchValue << " was NOT FOUND\n";
    }
    searchValue = 40;
    nodePtr = ListSearch (searchValue, head );
    if (nodePtr != NULL) {
    cout << "Search value " << searchValue << " was FOUND\n";
    } else {
    cout << "Search value " << searchValue << " was NOT FOUND\n";
    }

    // Deleting and Printing...
    DeleteLastNode(&head);
    PrintList(head);
    DeleteLastNode(&head);
    PrintList(head);
    DeleteLastNode(&head);
    PrintList(head);
    DeleteLastNode(&head);
    PrintList(head);
    DeleteLastNode(&head);
    PrintList(head);
    return 0;
}

EDIT I fixed up the ListSearch function. It didn't give out the '.cpp stopped working" pop-up anymore. But, the output still isn't right and searchValue 10 comes out as not found.

Output:

[10]
[20]->[0]
[20]->[30]->[0]
[20]->[30]->[40]->[0]
[20]->[30]->[40]->[50]->[0]
Search value 10 was NOT FOUND
Search value 5 was NOT FOUND
Search value 40 was FOUND
[20]->[30]->[40]->[50]
[20]->[30]->[40]
[20]->[30]
[20]

--------------------------------
Process exited after 0.02802 seconds with return value 0
Press any key to continue . . .

Answer 1

Unfortunately I don't have enough reputation to post a comment so I will post this as an answer. I am not sure what error you are getting but there are some bugs in the code. The search function doesn't check for the end of the list ie test for NULL when walking the linked list. It needs to do this and I think separately do the value comparison then return the correct node.