如果您出于某种原因需要，我需要为实验室做些什么，但它不一定是必要的。 [注意：很多我的gui代码都不起作用，因为我只是从代码的其他部分复制和粘贴]。
说明： 编写面向对象的C ++程序来创建双向链接。每个节点都应该是 能够存储一个人的名字和姓氏，以及他们各自的年龄。初始化 列表有5个节点。该程序应包括允许用户使用的成员函数 打印出年龄小于用户输入值的所有节点（两者之一） 方向）。它还应该允许用户搜索特定人的姓名。这应该 能够输出列表的平均年龄。最后，它应该允许删除名称。 该程序应允许用户从菜单中选择。
#include <iostream>
#include <string>
using namespace std;
typedef string Elem; // list element type
class DNode { // doubly linked list node
private:
Elem elem; // node element value
DNode* prev; // previous node in list
DNode* next; // next node in list
friend class DLinkedList; // allow DLinkedList access
};
class DLinkedList { // doubly linked list
public:
DLinkedList(); // constructor
~DLinkedList(); // destructor
bool empty() const; // is list empty?
const Elem& front() const; // get front element
const Elem& back() const; // get back element
void addFront(const Elem& name); // add to front of list
void addBack(const Elem& name); // add to back of list
void removeFront(); // remove from front
void removeBack(); // remove from back
void displayViaAge();
void displayViaName();
private: // local type definitions
DNode* header; // list sentinels
DNode* trailer;
protected: // local utilities
void add(DNode* v, const Elem& name); // insert new node before v
void remove(DNode* v); // remove node v
};
DLinkedList::DLinkedList() { // constructor
header = new DNode; // create sentinels
trailer = new DNode;
header->next = trailer; // have them point to each other
trailer->prev = header;
}
DLinkedList::~DLinkedList() { // destructor
while (!empty()) removeFront(); // remove all but sentinels
delete header; // remove the sentinels
delete trailer;
}
// insert new node before v
void DLinkedList::add(DNode* v, const Elem& name) {
DNode* u = new DNode; u->elem = name; // create a new node for e
u->next = v; // link u in between v
u->prev = v->prev; // ...and v->prev
v->prev->next = v->prev = u;
}
void DLinkedList::addFront(const Elem& name) // add to front of list
{ add(header->next, name); }
void DLinkedList::addBack(const Elem& name) // add to back of list
{ add(trailer, name); }
void DLinkedList::remove(DNode* v) { // remove node v
DNode* u = v->prev; // predecessor
DNode* w = v->next; // successor
u->next = w; // unlink v from list
w->prev = u;
delete v;
}
void DLinkedList::removeFront() // remove from font
{ remove(header->next); }
void DLinkedList::removeBack() // remove from back
{ remove(trailer->prev); }
bool DLinkedList::empty() const // is list empty?
{ return (header->next == trailer); }
const Elem& DLinkedList::front() const // get front element
{ return header->next->elem; }
const Elem& DLinkedList::back() const // get back element
{ return trailer->prev->elem; }
void DLinkedList::displayViaAge() { //Displays person via age
DNode*temp = header;
while(temp!=trailer)
{
//if(howold = age)
cout << temp->elem <<endl;
temp = temp -> next;
}
cout << temp->elem<<endl;
}
int main(){
char input = 'z';
string entry;
int age;
DLinkedList person;
person.addFront("Takkun Bradly");
person.add("Devindra Ardnived");
person.add("SeboY Wang");
person.add("DoubleX Slash");
person.add("Uncle Jelly");
cout << "What would you like to do?" << endl;
cout << "Enter 'A' to: Add a new person" << endl;
cout << "Enter 'B' to: Remove a person" << endl;
cout << "Enter 'C' to: Search for people via age" << endl;
cout << "Enter 'D' to: Search for people via name" << endl;
cout << "Enter 'E' to: Average all the total ages" << endl;
cout << "Enter 'F' to: Quit" << endl;
while(input != 'f') {
cin >> input;
cout << endl;
while ((input != 'a')&&(input != 'b')&&(input != 'c')&&(input != 'd')&&(input != 'e')&&(input != 'f')) {
cout << "Please enter a valid selection" << endl;
cin >> input;
}
if ((input == 'a')){
cout << "Please enter their name: ";
cin.ignore();
getline(cin, entry);
cout << "Please enter their age: ";
cin >> age;
person.addFront(entry);
}
if ((input == 'b')){
cout << "Who would you like to remove: ";
cin.ignore();
getline(cin, entry);
person.removeFront();
}
if ((input == 'c')){
cout << "What is the age of the person you are looking for?: ";
person.displayViaAge();
}
if ((input == 'd')){
cout << "What is the name of the person you are looking for?: ";
cin.ignore();
getline(cin, entry);
person.addFront(entry);
}
if ((input == 'e')){
return 0;
}
cout << endl;
}
}
答案 0 :(得分：1)
我认为你的错误在你的添加方法的这一行：
v->prev->next = v->prev = u;
此行中的此分配将从右向左执行。因此v->prev设置为u，然后v->prev->next设置为v->prev，现在指向u。所以现在你u->next指向u，这不是你想要的。
我认为你想要这样的东西：
// insert new node before node v
void DLinkedList::add(DNode* v, const Elem& name) {
DNode* u = new DNode; u->elem = name; // create a new node and set name
u->next = v; // make v the successor of u
u->prev = v->prev; // set u's predecessor to v's current predecessor
u->prev->next = u; // make u the successor of v's predecessor
v->prev = u; // finally make u the predecessor of v
}