[英]Segmentation Fault because of Pointers
我一直遇到很多麻煩,因為我忘記了所有指針規則。 我3年前了解了指針,從那以后就再沒有使用過。 我在LinkedList.cpp文件中添加的函數的行contents -> setPrevious(&node)
中收到分段錯誤。 我相信這與調用setPrevious函數或將節點作為指針傳遞有關。 任何幫助都會很棒。 謝謝!
LinkedList.h
#ifndef LINEARNODE_H
#define LINEARNODE_H
#include<iostream>
using namespace std;
class LinearNode
{
public:
//Constructor for the LinearNode class that takes no arguments
LinearNode();
//Constructor for the LinearNode class that takes the element as an argument
LinearNode(int el);
//returns the next node in the set.
LinearNode* getNext();
//returns the previous node in the set
LinearNode* getPrevious();
//sets the next element in the set
void setNext(LinearNode* node);
//sets the previous element in the set
void setPrevious(LinearNode* node);
//sets the element of the node
void setElement(int el);
//gets the element of the node
int getElement();
private:
LinearNode* next;
LinearNode* previous;
int element;
};//ends the LinearNode class
#endif
LinkedList.cpp
#include<iostream>
#include"LinearNode.h"
#include"LinkedList.h"
using namespace std;
//linkedlist constructor for an empty linked list
LinkedList::LinkedList()
{
count = 0;
contents = NULL;
}//ends the constructor
//adds an element to the front of the linked list
void LinkedList::add(int element)
{
int found = 0, current = 0;
for (int index = 0; index < count; index++)
{
if (contents -> getElement() == element)
found = 1;
else
{
contents = contents -> getNext();
}//ends the else statement
}//ends the while loop
if ((found == 0) && (count == 0))
{
LinearNode node;
node.setElement(element);
contents = &node;
count++;
print();
}//ends the if statement
else
{
LinearNode node;
node.setElement(element);
node.setNext(contents);
contents -> setPrevious(&node);
contents = &node;
count++;
//print();
cout << endl;
}//ends the found == 0 if statment
}//ends the add function
//this function removes one element from the linked list.
int LinkedList::remove(int element)
{
int found = 0, result = 0;
LinearNode* previous;
LinearNode* current;
if (count == 0)
cout << "The list is empty" << endl;
else
{
if (contents -> getElement() == element)
{
result = contents -> getElement();
contents = contents -> getNext();
}//ends the contents.getElement() == element
else
{
previous = contents;
current = contents -> getNext();
for (int index = 0; ( (index < count) && (found == 0) ); index++)
if (current -> getElement() == element)
found = 1;
else
{
previous = current;
current = current -> getNext();
}//ends the else statement
if (found == 0)
cout << "The element is not in the list" << endl;
else
{
result = current -> getElement();
previous -> setNext(current -> getNext());
}//ends else statement
}//ends the else stamtement
count--;
}//ends the else statement of count == 0
return result;
}//ends the remove function
void LinkedList::print()
{
LinearNode* current;
current = contents;
for (int index = 0; index < count; index++)
{
cout << current -> getElement() << endl;
current = current -> getNext();
}//ends the for loop
}//ends Print function
LinearNode.h
#ifndef LINEARNODE_H
#define LINEARNODE_H
#include<iostream>
using namespace std;
class LinearNode
{
public:
//Constructor for the LinearNode class that takes no arguments
LinearNode();
//Constructor for the LinearNode class that takes the element as an argument
LinearNode(int el);
//returns the next node in the set.
LinearNode* getNext();
//returns the previous node in the set
LinearNode* getPrevious();
//sets the next element in the set
void setNext(LinearNode* node);
//sets the previous element in the set
void setPrevious(LinearNode* node);
//sets the element of the node
void setElement(int el);
//gets the element of the node
int getElement();
private:
LinearNode* next;
LinearNode* previous;
int element;
};//ends the LinearNode class
#endif
LinearNode.cpp
#include<iostream>
#include"LinearNode.h"
using namespace std;
//Constructor for LinearNode, sets next and element to initialized states
LinearNode::LinearNode()
{
next = NULL;
element = 0;
}//ends LinearNode default constructor
//Constructor for LinearNode takes an element as argument.
LinearNode::LinearNode(int el)
{
next = NULL;
previous = NULL;
element = el;
}//ends LinearNode constructor
//returns the next element in the structure
LinearNode* LinearNode::getNext()
{
return next;
}//ends getNext function
//returns previous element in structure
LinearNode* LinearNode::getPrevious()
{
return previous;
}//ends getPrevious function
//sets the next variable for the node
void LinearNode::setNext(LinearNode* node)
{
next = node;
}//ends the setNext function
//sets previous for the node
void LinearNode::setPrevious(LinearNode* node)
{
previous = node;
}//ends the setPrevious function
//returns element of the node
int LinearNode::getElement()
{
return element;
}//ends the getelement function
//sets the element of the node
void LinearNode::setElement(int el)
{
element = el;
}//ends the setElement function
LinearNode node;
node.setElement(element);
contents = &node;
count++;
這將在堆棧上創建一個LinearNode,使contents
指向該節點,將作用域保留在下面的}
(使node
無效),然后contents
指向無效數據。
您需要重新考慮整個類-鏈表需要堆存儲,因此您必須使用new
和delete
來源中還有其他幾個錯誤,但是您應該首先解決這個基本的誤解,然后在需要時再提出一個更新的問題。
其他一些錯誤:
問題是您沒有在堆中分配Node,而僅在堆棧中。
在添加功能
LinearNode node;
node.setElement(element);
contents = &node;
count++;
應該:
LinearNode* node = new LinearNode;
node->setElement(element);
contents = node;
count++;
尋找每個小問題都需要經過很多代碼,但LinkedList :: add()會跳出一件不好的事情。 在這里,您在堆棧上聲明了“節點”,然后設置了一個指向它的指針。 當add()返回時,指向的對象將變為垃圾箱-調用析構函數。 這種事情很快導致了段錯誤。
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