看到这周的作业题之后google了一下，然后果断是想多了，一直在考虑这个双向的list到底要怎么实现，啊 总之是想太多了，其实之前还想着头和尾遇到啊什么的你的prev指向我我的next再指向你，然后头和尾的prev、next要不要换方向什么的。。。结果＝ ＝ 想多了。。。很自然的一个list。。双向的而已。。
上学期指针学的太渣了，最近虽然作业一直都在，不过还是把这个写完了才理解的更清楚一点。。。
另外。。简直是血的教训深刻领悟了内存的问题。。。今天被两个大大嘲笑了T。T：“一年之后还是小白。。。。”。论NULL的必要性！！而且搞懂了内存，虚拟内存，硬盘啊什么的，其实我这种零基础的导论课本当初应该好好研究的。。T.T，只要一点击运行，我的编译器就开始卡，往死里卡，我在这期间写完了高数作业 ＝ ＝ 最后系统告诉我qq和xcode都被迫暂停了，重启之后我看我的硬盘的存储空间还有39G，再一运行就23G了。。之后问了下师兄，然后在点运行之后监测我的内存变化，惊呆了！几秒钟就变到2.03G，然后再一看硬盘是32G（重启之后从39G开始变化的），然后我才搞清楚。。。哦。。忘记说原因了。。。少了一行代码。。。没有把头的prev和尾的next设为NULL！
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题干里给的头文件Doulist.h
#ifndef SSCPP2014_DOULIST_A_H
#define SSCPP2014_DOULIST_A_H
#include <string>
struct DouListNode {
int elem;
DouListNode *prev, *next;
DouListNode(int e = 0, DouListNode *p = 0, DouListNode *n = 0) {
elem = e;
prev = p;
next = n;
}
};
class DouList {
private:
DouListNode *m_head, *m_tail;
public:
DouList();
DouList(const DouList &src);
~DouList();
void clear();
bool empty() const;
std::string to_str() const;
int front() const;
int back() const;
void push_front(const int &e);
void push_back(const int &e);
void pop_front();
void pop_back();
void operator=(const DouList &other);
friend std::ostream& operator<<(std::ostream &out,
const DouList &list);
// non-meaning static value
staticint _error_sign; // for illegal front()/back()
};
#endif
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
题干里给的main函数
#include <iostream>
#include "DouList.h"
usingnamespacestd;
DouList list1, list2;
void display() {
cout << list1.empty() << ‘:‘ << list1 << endl;
cout << list2.empty() << ‘:‘ << list2.to_str() << endl;
}
int main() {
display();
list1.push_front(894);
list2.push_back(2136);
cout << list1.front() << ‘,‘ << list1.back() << endl;
cout << list2.front() << ‘,‘ << list2.back() << endl;
display();
list1.push_back(214);
list2.push_front(931);
cout << list1.front() << ‘,‘ << list1.back() << endl;
cout << list2.front() << ‘,‘ << list2.back() << endl;
display();
for (int i = 0; i < 10; ++i) {
int t;
cin >> t;
list1.push_back(t);
list2.push_front(t);
}
display();
cout<<"###\n";
for (int i = 0; i < 5; ++i) {
list1.pop_front();
list2.pop_back();
}
display();
DouList list3(list1);
list1 = list2;
cout << list1 << endl;
cout << list3 << endl;
return 0;
}
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我忧伤的cpp。。。
#include "DouList.h"
#include <string>
#include<iostream>
usingnamespacestd;
int DouList:: _error_sign = -1;
DouList::DouList() {
m_head = NULL;
m_tail = NULL;
}
DouList::DouList(const DouList &src) {
m_head = NULL;
m_tail = NULL;
DouListNode *temp = src.m_head;
DouListNode *p = NULL;
if (temp != NULL) {
m_head = new DouListNode(temp->elem, NULL, NULL);
p = m_head;
temp = temp->next;
}
while (temp != NULL) {
p->next = new DouListNode(temp->elem, p, NULL);
temp = temp->next;
p = p->next;
}
m_tail = p;
// *this = src; ta给的标程一句话就好 T.T
}
DouList::~DouList() {
clear();
}
void DouList::clear() {
while (m_head != NULL) {
DouListNode *a = m_head;
m_head = m_head->next;
delete a;
}
m_head = NULL;
m_tail = NULL;
}
bool DouList::empty() const {
if ((m_tail == m_head) &&(m_head == NULL)){
return true;
} else {
returnfalse;
}
}
string DouList::to_str() const {
string output;
if (this->empty() == true) {
output = "[]";
} else {
output = "[";
DouListNode *p = m_head->next;
long long a = m_head->elem; // ta说按c＋＋11的标准，此处必须用long long !..
output += to_string(a);
while (p != NULL) {
a = p->elem;
output += ", " + to_string(a);
p = p->next;
}
output += "]";
}
return output;
}
int DouList::front() const {
returnm_head->elem;
}
int DouList::back() const {
returnm_tail->elem;
}
void DouList::push_front(const int &e) {
if (m_head == NULL) {
m_head = new DouListNode(e, NULL, NULL);
m_tail = m_head;
} else {
m_head->prev = newDouListNode( e, NULL, m_head);
m_head = m_head->prev;
}
}
void DouList:: push_back(const int &e) {
if (m_tail == NULL) {
m_tail = new DouListNode(e, NULL, NULL);
m_head = m_tail;
} else {
m_tail->next = newDouListNode( e, m_tail, NULL);
m_tail = m_tail->next;
}
}
void DouList::pop_front() {
if (m_head != NULL) {
DouListNode *a = m_head;
m_head = a->next;
m_head->prev = NULL; // ！！！！就是这
delete a;
}
}
void DouList::pop_back() {
if(m_tail != NULL) {
DouListNode *a = m_tail;
m_tail = m_tail->prev;
m_tail ->next = NULL; // ！！！还有这
delete a;
}
}
voidDouList::operator=(constDouList &other) {
this->clear();
m_head = m_tail = NULL;
if (other.empty())
return;
m_head = newDouListNode(other.m_head->elem);
DouListNode *p = m_head;
DouListNode *q = other.m_head->next;
while (q) {
p->next = new DouListNode(q->elem, p);
p = p->next;
q = q->next;
}
m_tail = p;
}
ostream& operator<<(ostream &out,const DouList &list) {
out << list.to_str();
return out;
}
看硬盘刷刷刷就没了还是蛮好玩的哈哈哈哈。。。＝ ＝ 。。还是挺有收获的。。写谢谢讲代码的室友和“嘲笑”我的大大们和讲解的大大。。。。。
实现doubly-linked list&&搞清楚了一个内存问题,布布扣,bubuko.com
实现doubly-linked list&&搞清楚了一个内存问题
原文：http://www.cnblogs.com/SunnyInSysu/p/3667712.html