双头链表的实现

• // List.h
• #ifndef SSCPP2014_DOULIST_A_H
• #define SSCPP2014_DOULIST_A_H
•  
• #include<string>
•  
• structDouListNode{
• int elem;
• DouListNode*prev,*next;
• DouListNode(int e =0,DouListNode*p =0,DouListNode*n =0){
• elem = e;
• prev = p;
• next = n;
• }
• };
•  
• classDouList{
• private:
• DouListNode*m_head,*m_tail;
• public:
• DouList();
• DouList(constDouList&src);
• ~DouList();
• void clear();
• bool empty()const;
• std::string to_str()const;
• int front()const;
• int back()const;
• void push_front(constint&e);
• void push_back(constint&e);
• void pop_front();
• void pop_back();
• voidoperator=(constDouList&other);
• friend std::ostream&operator<<(std::ostream &out,
• constDouList&list);
• // non-meaning static value
• staticint _error_sign;// for illegal front()/back()
• };
•  
• #endif
•  
•  
•  
•  
•  
•  
• // List.cpp

• #include<iostream>
  #include<string>
  #include "DouList.h"
  using namespace std;

  DouList::DouList() {
  m_head = m_tail = NULL;
  }

  DouList::DouList(const DouList &src) {
  m_head = m_tail = NULL;
  *this = src;
  }

  DouList::~DouList() {
  clear();
  }

  void DouList::clear() {
  DouListNode *temp;
  while (m_head != NULL) {
  temp = m_head;
  m_head = m_head->next;
  delete temp;
  }
  m_head = m_tail = NULL;
  }

  bool DouList::empty() const {
  return (m_head == NULL && m_tail == NULL);
  }

  std::string DouList::to_str() const {
  DouListNode *t = m_head;
  string strtemp;
  strtemp += "[";
  if (m_head == NULL) {
  } else if (m_head == m_tail) {
  int i = 0, x = t->elem, ch[10] = {0};
  if (x == 0) {
  strtemp.push_back('0');
  } else {
  while (x) {
  ch[i] = x % 10;
  x /= 10;
  i++;
  }
  for (int j = i-1; j >= 0; j--) {
  strtemp.push_back(ch[j] + '0');
  }
  }
  } else {
  while (t->next != NULL) {
  int i = 0, x = t->elem, ch[10] = {0};
  if (x == 0) {
  strtemp.push_back('0');
  strtemp += ", ";
  t = t->next;
  } else {
  while (x) {
  ch[i] = x % 10;
  x /= 10;
  i++;
  }
  for (int j = i-1; j >= 0; j--) {
  strtemp.push_back(ch[j] + '0');
  }
  strtemp += ", ";
  t = t->next;
  }
  }
  int i = 0, x = t->elem, ch[10] = {0};
  if (x == 0) {
  strtemp.push_back('0');
  } else {
  while (x) {
  ch[i] = x % 10;
  x /= 10;
  i++;
  }
  for (int j = i-1; j >= 0; j--) {
  strtemp.push_back(ch[j] + '0');
  }
  }
  }
  strtemp += "]";
  return strtemp;
  }

  int DouList::front() const {
  return m_head->elem;
  }

  int DouList::back() const {
  return m_tail->elem;
  }

  void DouList::push_front(const int &e) {
  if (m_head == NULL && m_tail == NULL) {
  DouListNode *temp = new DouListNode(e);
  m_head = temp;
  m_tail = temp;
  } else {
  DouListNode *temp = new DouListNode(e);
  temp->next = m_head;
  temp->prev = NULL;
  m_head->prev = temp;
  m_head = temp;
  }
  }

  void DouList::push_back(const int &e) {
  if (m_head == NULL && m_tail == NULL) {
  DouListNode *temp = new DouListNode(e);
  m_head = temp;
  m_tail = temp;
  } else {
  DouListNode *temp = new DouListNode(e);
  temp->prev = m_tail;
  temp->next = NULL;
  m_tail->next = temp;
  m_tail = temp;
  }
  }

  void DouList::pop_front() {
  if (empty()) {
  return;
  }
  if (m_head == m_tail) {
  clear();
  return;
  } else {
  DouListNode *temp = m_head;
  m_head = m_head->next;
  m_head->prev = NULL;
  delete temp;
  }
  }

  void DouList::pop_back() {
  if (empty()) {
  return;
  }
  if (m_head == m_tail) {
  clear();
  return;
  } else {
  DouListNode *temp = m_tail;
  m_tail = m_tail->prev;
  m_tail->next = NULL;
  delete temp;
  }
  }

  void DouList::operator=(const DouList &other) {
  clear();
  DouListNode *temp2 = other.m_head;
  DouListNode *temp = m_head = new DouListNode(temp2->elem);
  temp2 = temp2->next;
  while (temp2 != NULL) {
  temp->next = new DouListNode(temp2->elem, temp);
  temp = temp->next;
  temp2 = temp2->next;
  }
  m_tail = temp;
  }

  std::ostream& operator<<(std::ostream &output, const DouList &list) {
  output << list.to_str();
  return output;
  }