程序跳过std::getline

Program skips over std::getline

本文关键字：getline std 程序更新时间：2023-10-16

我必须设计一个程序，允许用户在一个双重链表中输入5个节点的信息，然后按字母顺序对双重链表进行排序。它跳过了允许用户输入地址，不打印除姓名以外的任何信息，也不按字母顺序排序列表。我做错了什么?

#include <iostream>
#include <string>
struct node
{
    std::string firstName;
    std::string lastName;
    std::string address;
    long phoneNum;
    node *next;
    node *prev;
};
bool isEmpty(node *head);
void insertAsFirstElement(node *&head, node *&last, std::string firstName, std::string lastName, std::string address, long phoneNum);
void insert(node *&head, node *&last, std::string firstName, std::string lastName, std::string address, long phoneNum);
void searchFor(node *&last, std::string lastName);
void showList(node *current);

bool isEmpty(node *head)
{
    if(head == NULL)
        return true;
    else
        return false;
}

void insertAsFirstElement(node *&head, node *&last, std::string firstName, std::string lastName, std::string address, long phoneNum)
{
    node *temp = new node;
    temp->firstName = firstName;
    temp->lastName = lastName;
    temp->address = address;
    temp->phoneNum;
    temp->next = NULL;
    temp->prev = NULL;
    head = temp;
    last = temp;
}
void insert(node *&head, node *&last, std::string firstName, std::string lastName, std::string address, long phoneNum)
{
    if(isEmpty(head))
        insertAsFirstElement(head, last, firstName, lastName, address, phoneNum);
    else
    {
        node *temp = new node;
        temp->firstName = firstName;
        temp->lastName = lastName;
        temp->address = address;
        temp->phoneNum;
        int result = lastName.compare(last->lastName);
        if (result < 0)
        {
            temp->next = head;
            head->prev = temp;
            temp->prev = NULL;
            head = temp;
        }
        else if ( result > 0)
        {
            temp->next = NULL;
            temp->prev = last;
            last->next = temp;
            last = temp;
        }
    }
}
void searchFor(node *&last, std::string findName)
{
    node *temp = last;
    while (temp != NULL)
    {
        if (temp->lastName == findName)
        {
            std::cout << temp->firstName << " " << temp->lastName << " " << temp->address << " " << temp->phoneNum << std::endl;;
        }
        temp = temp->prev;
    }
}

void showList(node *current)
{
    if(isEmpty(current))
        std::cout << "The list is emptyn";
    else
    {
        std::cout << "The list contains: n";
        while(current != NULL)
        {
            std::cout << current->firstName << " " << current->lastName << " " << current->address << " " << current->phoneNum << std::endl;
            current = current->next;
        }
     } 
}
int main()
{
    node *head = NULL;
    node *last = NULL;
    std::string firstName;
    std::string lastName;
    std::string address;
    long phoneNum;
    int count;
    count = 5;
    while (count > 0)
    {
        std::cout << "Enter the first name of person #" << count << ":n";
        std::cin >> firstName;
        std::cout << "Enter the last name of person #" << count << ":n";
        std::cin >> lastName;
        std::cout << "Enter the address of person #" << count << ":n";
        std::getline(std::cin,address);
        std::cout << "Enter the phone number of person #" << count << ":n";
        std::cin >> phoneNum;
        insert(head, last, firstName, lastName, address, phoneNum);
        count = count - 1;
     } 
    showList(head);
    std::string findName;
    std::cout << "What is the last name of the person you would like to find?n";
    std::cin >> findName;
    searchFor(last, findName);
    return 0; 
}

你的问题是你混合了cin >>和getline，这在c++中是有问题的，因为尾随换行符等等。

好的做法是始终使用getline，然后使用stringstream将行拆分为令牌。例如，我修改了您的解决方案，仅使用getline和字符串流(注意:您需要在文件的顶部添加#include <sstream>。

你可以在这里阅读更多关于混合cin >>和getline的问题以及其他解决方法。

int main()
{
    node *head = NULL;
    node *last = NULL;
    std::string firstName;
    std::string lastName;
    std::string address;
    std::string phoneNumStr;
    long phoneNum;
    int count;
    count = 5;
    while (count > 0)
    {
        std::cout << "Enter the first name of person #" << count << ":n";
        std::getline(std::cin,firstName);   // no use of cin >>
        std::cout << "Enter the last name of person #" << count << ":n";
        std::getline(std::cin,lastName);    // no use of cin >>
        std::cout << "Enter the address of person #" << count << ":n";
        std::getline(std::cin,address);
        std::cout << "Enter the phone number of person #" << count << ":n";
        std::getline(std::cin,phoneNumStr);
        std::stringstream s(phoneNumStr);    // no use of cin. Using stringstream to break up line and extract it into phoneNum
        s >> phoneNum;
        insert(head, last, firstName, lastName, address, phoneNum);
        count = count - 1;
     }
    showList(head);
    std::string findName;
    std::cout << "What is the last name of the person you would like to find?n";
    std::cin >> findName;
    searchFor(last, findName);
    return 0;
}