C++ 代碼可以編譯，但在運行時出現分段錯誤。 我想我正在修改鏈表

Question

大家好，先在這里發帖。 所以它進入周末，我無法訪問我的課程講師。 這是我們第一個使用鏈表的項目，我對它進行了很好的處理。 錯誤是，我很確定，在 sl_list.cpp output << temp -> contents();第 53 行output << temp -> contents(); 這是為了訪問節點的內容，在這種情況下是一個 int，並將它存儲在一個 stringstream 變量中，以便我可以稍后輸出整個內容。 顯然我做得不對。 我一直在嘗試修復它一天半的大部分時間，但我只是不知道我做錯了什么。 所有以“sl”開頭的文件都是我的，export_18.cpp 是我的導師創建的測試代碼。 如果我注釋掉有問題的函數，我的代碼將按預期編譯和運行。 這里有人能告訴我我搞砸了什么嗎？ 它可能很容易被發現。 謝謝你。

#include "sl_list.h"
#include <iostream>
#include <sstream>
using namespace std;
using std::stringstream;

SLList::SLList() {  // Sets head_ to NULL and size_ to 0
  head_ = NULL;
  size_ = 0;
}
SLList::~SLList() {  // Destructor for SLList
}
void SLList::InsertHead(int number) {  // Creates new dynamic SLNode
  SLNode* to_insert = new SLNode(number);
  to_insert -> set_next_node(head_);
  head_ = to_insert;
  size_++;
}
void SLList::RemoveHead() {  // Remove the SLNode from the list
  if (head_ != NULL) {  // Check for NULL
    SLNode* temp = head_;  // Storage for temp location
    head_ = head_ -> next_node();  // Set head to next_node
    delete temp;  // Delete temp storage
    size_--;  // Decrement size
  }
}
void SLList::Clear() {  // Clear the entire contents of the list
  if (head_ != NULL) {  // Check for NULL
    while (head_ != NULL) {  // Check for NULL
      SLNode* temp = head_;  // Storage for temp location
      head_ = head_ -> next_node();  // Set head to next_node
      delete temp;  // Delete temp storage
      size_--;  // Decrement size
    }
  }
}
unsigned int SLList::size() const {  // return size_
  return size_;
}
string SLList::ToString() const {  // returns the contents of all nodes
  if (head_ != NULL) {  // Check for NULL
    stringstream output;  // Storage for stringstream
    SLNode* temp = head_;  // Storage for temp location
      while (temp != NULL) {  // Check for NULL
        temp = temp -> next_node();  // Set head to next_node
        output << temp -> contents();  // Dumping temp into output
        if (temp != NULL) {  // Add a space and comma to the end of output
          output << ", ";
        }
      }
    return output.str();  // Return output
  } else {
    return "";  // If head_ was NULL return empty string
  }
}

---

#ifndef SL_LIST_H
#define SL_LIST_H

#include "sl_node.h"
#include <iostream>
using std::string;

class SLList {
 public:
  SLList();  // Default constructor
  ~SLList();  // Default destructor
  void InsertHead(int number);  // Creates new dynamic SLNode
  void RemoveHead();  // Remove the SLNode from the list
  void Clear();  // clear the entire contents of the list
  unsigned int size() const;  // Return size_
  string ToString() const;  // returns the contents of all nodes

 private:
  SLNode* head_;  // Storage for the next node locations
  unsigned int size_;  // Storage for the size
};

#endif /* SL_LIST.H */

---

#include "sl_node.h"
#include <iostream>

SLNode::SLNode() {  // Default constructor
  next_node_ = NULL;
  contents_ = 0;
}

SLNode::SLNode(unsigned int contents) {  // overloaded constructor
  next_node_ = NULL;
  contents_ = contents;
}

SLNode::~SLNode() {  // Empty destructor
}

void SLNode::set_contents(int contents) {  // Set contents_ to contents
  contents_ = contents;
}

int SLNode::contents() const {  // Return contents_
  return contents_;
}

void SLNode::set_next_node(SLNode* next_node) {  // Sets location of next node
  next_node_ = next_node;
}

SLNode* SLNode::next_node() const {  // Return next_node_
  return next_node_;
}

---

#ifndef SL_NODE_H
#define SL_NODE_H

class SLNode {
 public:
  SLNode();  // Default constructor
  SLNode(unsigned int contents);  // Overloaded constructor
  ~SLNode();  // Empty destructor
  void set_contents(int contents);  // Set contents_ to contents
  int contents() const;  // Return contents_
  void set_next_node(SLNode* next_node);  // Sets location of next node
  SLNode* next_node() const;  // Return next_node_

 private:
  SLNode* next_node_;  // Storage for the next node locations
  int contents_;  // Storage for the contents of the node
};

#endif /* SL_NODE.H */

---

#include "sl_list.h"
#include "sl_node.h"
#include <sstream>
#include <iostream>
using std::cout;
using std::endl;
using std::string;
using std::stringstream;

// For testing (DO NOT ALTER)
void Test(bool test, string more_info = "");
void UnitTest();

// Program Execution Starts Here
int main() {
  // To test your code (DO NOT ALTER)
  UnitTest();
  // This ends program execution
  return 0;
}

// For testing (DO NOT ALTER)
void UnitTest() {
  string temp = "This unit test will test some of your code:\n";
  cout << temp << string(temp.length() - 1, '-') << endl;
  // Tests
  SLList list;
  stringstream full_list, half_list;
  for (int i = 999; i > 0; i--) {
    full_list << i << ", ";
    if (i < 500)
      half_list << i << ", ";
  }
  full_list << 0;
  half_list << 0;

  Test(list.size() == 0, "Default Constructor & size()");
  Test(list.ToString() == "", "ToString()");

  list.RemoveHead();
  Test(list.size() == 0, "RemoveHead() & size()");

  list.InsertHead(1);
  Test(list.size() == 1, "InsertHead(1) & size()");
  Test(list.ToString() == "1", "ToString()");

  list.RemoveHead();
  Test(list.size() == 0, "RemoveHead() & size()");
  Test(list.ToString() == "", "ToString()");

  list.InsertHead(10);
  list.InsertHead(20);
  Test(list.size() == 2, "InsertHead(10), InsertHead(20) & size()");
  Test(list.ToString() == "20, 10", "ToString()");

  list.RemoveHead();
  Test(list.size() == 1, "RemoveHead() & size()");
  Test(list.ToString() == "10", "ToString()");

  list.InsertHead(5);
  Test(list.size() == 2, "InsertHead(5) & size()");
  Test(list.ToString() == "5, 10", "ToString()");

  list.Clear();
  Test(list.size() == 0, "Clear() & size()");
  Test(list.ToString() == "", "ToString()");

  for (unsigned int i = 0; i < 1000; i++)
    list.InsertHead(i);
  Test(list.size() == 1000, "InsertHead() \"HIGH LOAD\" & size()");
  Test(list.ToString() == full_list.str(), "ToString()");

  for (unsigned int i = 0; i < 500; i++)
    list.RemoveHead();
  Test(list.size() == 500, "RemoveHead() \"HIGH LOAD / 2\" & size()");
  Test(list.ToString() == half_list.str(), "ToString()");
  for (unsigned int i = 0; i < 600; i++)
    list.RemoveHead();
  Test(list.size() == 0, "RemoveHead() \"HIGH LOAD / 2\" & size()");
  Test(list.ToString() == "", "ToString()");

  cout << string(temp.length() - 1, '-') << endl;
  cout << "Unit Test Complete!\n\n";
}

// For testing (DO NOT ALTER)
void Test(bool test, string more_info) {
  static int test_number = 1;
  if (test)
    cout << "PASSSED TEST ";
  else
    cout << "FAILED  TEST ";
  cout << test_number << " " << more_info << "!\n";
  test_number++;
}

Answer 1

在您的輸出循環中，您將 temp 移至下一個節點，然后再輸出其值。 只需交換這兩條線。

temp = temp -> next_node();  // Set head to next_node
output << temp -> contents();  // Dumping temp into output

應該成為

output << temp -> contents();  // Dumping temp into output
temp = temp -> next_node();  // Set head to next_node