我有一个程序接受带有 5 个参数的输入。输入是视频标题、url、评论、长度和评级。然后根据标题对它们进行排序。用户需要指定insert(输入视频信息)，lookup(按标题查找视频并仅打印该视频及其相关信息)，或打印(只需打印所有内容)。
例如
输入:
insert
Arthur Benjamin: Lightning calculation and other "Mathemagic"
http://www.youtube.com/watch?v=M4vqr3_ROIk
Hard to believe.
15.25
4
lookup
Arthur Benjamin: Lightning calculation and other "Mathemagic"
输出:
Arthur Benjamin: Lightning calculation and other "Mathemagic" , http://www.youtube.com/watch?v=M4vqr3_ROIk, Hard to believe., 15.25, 4
我的问题是处理 main 中的lookup
if(user == "lookup")
{
getline(cin, title);
if(vlistObj -> lookup(videoObj))
{
vlistObj->print();
}
}
还有在我的链接列表中查找
bool Vlist::lookup(Video *other)
{
Node *node = m_head;
return node->m_next -> m_video->GetTitle() == other-> GetTitle();
}
老实说，我很迷茫如何查找搜索特定标题(假设已经给出了很多视频标题/信息)并且只打印我要求的内容(假设它在列表中) .
完整代码如下:
#include <iostream>
#include <stdlib.h>
#include <cstring>
using namespace std;
class Video {
public:
Video(string video_title, string video_link, string video_comment, double video_length, int video_number);
void print();
const string& GetTitle() const { return title; }
private:
std::string title;
string link;
string comment;
double length;
int rating;
};
Video::Video(string video_title, string video_link, string video_comment, double video_length, int video_number)
: title(video_title), link(video_link), comment(video_comment), length(video_length), rating(video_number)
{
}
void Video::print(){
cout << title << ", " << link << ", " << comment << ", " << length << ", " << rating << endl;
}
class Vlist {
public:
Vlist() {m_head = nullptr; }
bool lookup(Video *other);
void Insert(Video *video);
void print();
private:
class Node {
public:
Node(Video *video, Node *next) {m_video = video; m_next = next; }
Video *m_video;
Node *m_next;
};
Node *m_head;
};
void Vlist::Insert(Video* video)
{
if (m_head == NULL || m_head->m_video -> GetTitle() > video->GetTitle())
{
m_head = new Node(video, m_head);
}
else
{
Node *node = m_head;
while (node->m_next != NULL && node->m_next -> m_video->GetTitle() < video->GetTitle())
{
node = node->m_next;
}
node->m_next = new Node(video, node->m_next);
}
}
bool Vlist::lookup(Video *other)
{
Node *node = m_head;
return node->m_next -> m_video->GetTitle() == other-> GetTitle();
}
void Vlist::print()
{
Video *video;
Node *node = m_head;
while(node != NULL)
{
node -> m_video-> Video::print();
node = node->m_next;
}
}
int main()
{
string sort_type, url, comment, title, user;
int rating;
double length;
int initial = 0, last = 0, number;
Vlist *vlistObj= new Vlist();
Video *videoObj;
while (getline(cin,user)) {
if(user == "insert")
{
getline(cin,title);
getline(cin, url);
getline(cin, comment);
cin >> length;
cin >> rating;
cin.ignore();
videoObj = new Video(title,url, comment, length, rating);
vlistObj->Insert(videoObj);
}
if(user == "lookup")
{
getline(cin, title);
if(vlistObj -> lookup(videoObj))
{
vlistObj->print();
}
}
if(user == "print")
{
vlistObj->print();
}
}
}
Also I do want to note that I am receiving a segmentation fault. But I do know that it is because of my code in lookup. The program runs and output correctly if I do not type lookup
最佳答案
错误在 Vlist::lookup 函数中，当前节点指针指向 m_next，然后指向 m_video: m_next不是必需的，m_head应该直接指向m_video。
在完整的工作代码下方，我还在这里和那里更改了一些内容以消除编译器的所有警告
#include <iostream>
#include <stdlib.h>
#include <cstring>
using namespace std;
class Video {
public:
Video(string video_title, string video_link, string video_comment, double video_length, int video_number);
void print();
const string& GetTitle() const { return title; }
private:
string title;
string link;
string comment;
double length;
int rating;
};
Video::Video(string video_title, string video_link, string video_comment, double video_length, int video_number)
: title(video_title), link(video_link), comment(video_comment), length(video_length), rating(video_number)
{
}
void Video::print(){
cout << title << ", " << link << ", " << comment << ", " << length << ", " << rating << endl;
}
class Vlist {
public:
Vlist():m_head(nullptr) {} // init_list
bool lookup(const string& title); // gets user input directly
void Insert(Video *video);
void print();
Video* get(const string& title); // new:returns pointer in list with given title
private:
class Node {
public:
Node(Video *video, Node *next):m_video(video), m_next(next) {} // init_list
Video *m_video;
Node *m_next;
} *m_head; // declared directly together with class definition
};
void Vlist::Insert(Video* video)
{
if (m_head == NULL || m_head->m_video -> GetTitle() > video->GetTitle())
{
m_head = new Node(video, m_head);
}
else
{
Node *node = m_head;
while (node->m_next != NULL && node->m_next -> m_video->GetTitle() < video->GetTitle())
{
node = node->m_next;
}
node->m_next = new Node(video, node->m_next);
}
}
bool Vlist::lookup(const string& title)
{
Node *node = m_head;
while (node->m_next != NULL && node-> m_video->GetTitle() != title)
{
node = node->m_next;
}
return node-> m_video->GetTitle() == title; // there was one pointer too many here
}
void Vlist::print()
{
Node *node = m_head;
while(node != NULL)
{
node -> m_video-> Video::print();
node = node->m_next;
}
}
Video* Vlist::get(const string& title) // returns required item from list
{
Node *node = m_head;
while (node != NULL) {
if (node->m_video->GetTitle() == title)
return node->m_video;
node = node->m_next;
}
return nullptr;
}
int main()
{
string sort_type, url, comment, title, user;
int rating;
double length;
Vlist *vlistObj= new Vlist;
Video *videoObj;
while (getline(cin,user)) {
if(user == "insert")
{
getline(cin,title);
getline(cin, url);
getline(cin, comment);
cin >> length;
cin >> rating;
cin.ignore();
videoObj = new Video(title, url, comment, length, rating);
vlistObj->Insert(videoObj);
}
if(user == "lookup") // more than a few changes here
{
getline(cin, title);
if (vlistObj -> lookup(title))
{
videoObj = vlistObj->get(title);
videoObj->print();
} else {
cout << "not found!\n";
}
}
if(user == "print")
{
vlistObj->print();
}
}
}
大编辑
以前的版本没有正确遍历 Vlist。
现在 lookup 命令正确搜索了 Vlist，从而最终打印出正确的 Video。
关于c++ - 如何在链表中搜索特定字符串并返回该值？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/64190137/