C++实现动态顺序表（vector）

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vector是连续存储结构，支持随机的高效的随机和在尾部进行插入、删除操作，其它位置的插入、删除操作相对来说效率较低。

vector相当于一个数组，但它的数组空间大小需要写一程序来实现。

它的内存分配原理大概可分为下面几步：

1）首先分配一块内存空间进行存储；
2）当所需存储的数据超过分配的空间时，再重新分配一块空间；
3）将旧元素复制到新空间；
4）释放旧空间。

实现代码如下：

vector.h

#pragma once

#include<stdio.h>
#include<assert.h>
#include<string.h>
#include<iostream>
using namespace std;

typedef int DataType;

class Vector
{
public:
 Vector()
  :_first(NULL),
  _finish(NULL),
  _endofstorage(NULL)
 {}

 Vector(const Vector& v){
  if (v.Size() > 0){
   _first = new DataType(v.Size());
   memcpy(_first, v._first, sizeof (DataType)*v.Size());
  }
  if (_first > 0){
   _finish = _first + v.Size();
   _endofstorage = _first + v.Size();
  }
  _first = _finish = _endofstorage = NULL;
 }

 Vector& operator=(const Vector& v){
  if (this != &v){
   /*swap(_first, v._first);
   swap(_finish, v._finish);
   swap(_endofstorage, v._endofstorage);*/

   DataType* tmp = new DataType(v.Size());
   memcpy(tmp, _first, sizeof(DataType)*v.Size());
   delete _first;
   _first = tmp;
   _finish = _first + v.Size();
   _endofstorage = _first + v.Size();
  }
  return *this;
 }

 ~Vector(){
  delete[] _first;
  _first = _finish = _endofstorage = NULL;
 }

 void Print(){
  DataType* cur = _first;
  while (cur != _first){
   cout << "*cur" << endl;
   cur++;
  }
  cout << endl;
 }

 size_t Size() const{
  return _finish - _first;
 }

 size_t Capacity() const{
  return _endofstorage - _first;
 }

 void Expand(size_t n){
  if (n > Capacity()){
   DataType* tmp = new DataType(n);
   size_t size = Size();
   memcpy(tmp, _first, sizeof(DataType)*size);
   delete[] _first;
   _first = tmp;
   _finish = _first + size;
   _endofstorage = _first + n;
  }
 }

 void PushBack(DataType x){
  if (_finish == _endofstorage){
   size_t capacity = Capacity() > 0 ? Capacity() * 2 : 3;
   Expand(capacity);
   /*if (Capacity() == 0){
    Expand(3);
   }
   else{
    Expand(Capacity() * 2);
   }*/
  }
  *_finish = x;
  ++_finish;
 }

 void PopBack(){
  assert(_finish > _first);
  --_finish;
 }

 void Reserve(size_t n){
  if (n > Capacity()){
   Expand(n);
  }
 }

 void Insert(size_t pos, DataType x){
  assert(pos < Size());
  if (_finish = _endofstorage){
   size_t capacity = Capacity() > 0 ? Capacity() * 2 : 3;
   Expand(capacity);
  }
  int tmp = Size() - 1;
  while (tmp >= (int)pos){
   _first[tmp + 1] = _first[tmp];
   --tmp;
  }
  _first[pos] = x;
  ++_finish;
 }

 void Erase(size_t pos){
  assert(pos < Size());
  size_t cur = pos;
  while (cur < Size()-1){
   _first[cur] = _first[cur] + 1;
   ++cur; 
  }
  --_finish;
 }

 size_t Find(DataType x){
  DataType *cur = _first;
  while (cur != _finish){
   if (*cur == x){
    return cur - _first;
   }
   ++cur;
  }
  return -1;
 }
private:
 DataType* _first;
 DataType* _finish;
 DataType* _endofstorage;
};

test.cpp

#include"vector.h"

void Tset(){
 Vector v;
 v.PushBack(1);
 v.PushBack(2);
 v.PushBack(3);
 v.PushBack(4);
 v.PopBack();
 v.Print();

 size_t pos = v.Find(1);
 printf("pos->data:expcet 1,axtual %lu", pos);

 Vector v1;
 v1.Insert(1, 0);
 v1.Print();

 Vector v2;
 v2.Erase(3);
 v2.Print();
}

int main(){
 Tset();
 return 0;
}

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