鏈表的一部分未打印

Question

因此，我正在處理鏈表代碼，我有兩個功能：一個向前構建列表，另一個向后構建列表。 我的代碼運行了，但是我遇到的問題是，它只打印出了buildlistForward()函數，而不是buildlistBackward()

#include <iostream>
#include <fstream>
using namespace std;

ifstream fin;
//ofstream fout;
struct nodeType
{
    int num;
    nodeType *next;
};
void buildlistForward();
void buildlistBackward();
//void deleteHead(nodeType);
int main()
{
    fin.open("testscores_input.txt");
    buildlistForward();
    buildlistBackward();

    return 0;
}
void buildlistForward()
{
    nodeType *head = NULL, *trail = NULL, *current = NULL;
    int digit;
    cout << "The list built forward is: " << endl;
    while (fin >> digit)
    {
        if (head == NULL)
        {
            head = new nodeType;
            head->num = digit;
            head->next = NULL;
            trail = head;
        }
        else
        {
            current = new nodeType;
            current->num = digit;
            current->next = NULL;
            trail->next = current;
            trail = current;
        }
    }
    current = head;
    while (current != NULL)
    {
        cout << current->num << endl;
        current = current->next;
    }
}
void buildlistBackward()
{
    nodeType *head1 = NULL, *current1;
    int digit;
    cout << "The list built backward is: " << endl;
    while (fin >> digit)
    {
        if (head1 == NULL)
        {
            head1 = new nodeType;
            head1->num = digit;
            head1->next = NULL;
        }
        else
        {
            current1 = new nodeType;
            current1->num = digit;
            current1->next = NULL;
            current1->next = head1;
            head1 = current1;
        }
    }
    current1 = head1;
    while (current1 != NULL)
    {
        cout << current1->num << endl;
        current1 = current1->next;
    }
}

Answer 1

該程序首先執行buildlistForward()因此，在讀取文件末尾時，對於buildlistBackward()沒有任何內容可讀取，您需要通過打開ifstream從文件中再次讀取，但是您也可以向后打印鏈接列表通過實現尾部，訪問最后一個node並從最后到第一打印每個node ，而不是在輸入每個節點時讀取輸入和打印。