标准模板库(STL)学习指南之vector向量

2021-10-27 10:24:44

vector

– 一. vector可以模拟动态数组

– 二. vector的元素可以是任意类型T，但必须具备赋值和拷贝能力（具有public

拷贝构造函数和重载的赋值操作符）

三.必须包含的头文件#include <vector>

– 四. vector支持随机存取

– 五. vector的大小（size）和容量（capacity）通常是不同的，size返回实际元素个数，

capacity返回vector能容纳的元素最大数量。如果插入元素时，元素个数超过capacity，

需要重新配置内部存储器。

->构造、拷贝和析构

->非变动操作

eg.

   vector<int> v1(10);
cout << "The capacity of v1 is " << v1.capacity() << endl;
cout << "The size of v1 is " << v1.size() << endl;

   vector<int> v2;

   v2.reserve(20);
cout << "The capacity of v2 is " << v2.capacity() << endl;
cout << "The size of v2 is " << v2.size() << endl;

output :

   The capacity of v1 is 10

   The size of v1 is 10

   The capacity of v2 is 20

   The size of v2 is 0

->赋值操作

所有的赋值操作都有可能调用元素类型的默认构造函数，拷贝构造函数，赋值操作符和析构函数

如:

std::list<T> l;

std::vector<T> v;

…

v.assign(l.begin(),l.end());

eg.

   vector<int> v;

   v.assign( 10, 42 );

   for( vector<int>::size_type i = 0; i < v.size(); i++ ) {
cout << v[i] << " ";

   }
cout << endl;

OutPut :

42 42 42 42 42 42 42 42 42 42

   vector<int> v1;

   for( int i = 0; i < 10; i++ ) {

     v1.push_back( i );

   }

 

   vector<int> v2;

   v2.assign( v1.begin(), v1.end() );

 

   for( vector<int>::size_type i = 0; i < v2.size(); i++ ) {
cout << v2[i] << " ";

   }

cout << endl;

output :

0 1 2 3 4 5 6 7 8 9

元素存取

标准模板库(STL)学习指南之vector向量

下面的操作是错误的:

std::vector<T> v;//empty

v[5]= t; //runtime error

std::cout << v.front(); //runtime error

eg.

vector<string> words;

    string str;

 

    while( cin >> str ) words.push_back(str);

 

    sort( words.begin(), words.end() );

 
cout << "In alphabetical order, the first word is '" << words.front() << "'." << endl;

假设输入是:  now is the time for all good men to come to the aid of their country

output:

In alphabetical order, the first word is 'aid'.

   vector<int> v;

   for( int i = 0; i < 5; i++ ) {

     v.push_back(i);

   }
cout << "The first element is " << v.front()

        << " and the last element is " << v.back() << endl;

output:

The first element is 0 and the last element is 4

迭代器相关函数

使用迭代器时应注意:

迭代器持续有效，除非发生以下两种情况：

1.) 或插入元素

2.) 容量变化而引起内存重新分配

eg.

    vector<string> words;

    string str;

 

    while( cin >> str ) words.push_back(str);

 

    for( vector<string>::const_iterator iter = words.begin();

         iter != words.end(); ++iter ) {
cout << *iter << endl;

    }

假设输入是 : hey mickey you're so fine

output:

hey

    mickey

    you're

    so

    fine

插入（insert）元素

eg.

   vector<char> alphaVector;

   for( int i=0; i < 10; i++ ) {

     alphaVector.push_back( i + 'A' );

   }

 

   // Insert four C's into the vector

   vector<char>::iterator theIterator = alphaVector.begin();

   alphaVector.insert( theIterator, 4, 'C' );

 

   // Display the vector

   for( theIterator = alphaVector.begin(); theIterator != alphaVector.end(); ++theIterator )    {
cout << *theIterator;

   }

output:

CCCCABCDEFGHIJ

    vector<int> v1;

    v1.push_back( 0 );

    v1.push_back( 1 );

    v1.push_back( 2 );

    v1.push_back( 3 );

 

    vector<int> v2;

    v2.push_back( 5 );

    v2.push_back( 6 );

    v2.push_back( 7 );

    v2.push_back( 8 );

 
cout << "Before, v2 is: ";

    for( vector<int>::size_type i = 0; i < v2.size(); i++ ) {
cout << v2[i] << " ";

    }
cout << endl;

 

    v2.insert( v2.end(), v1.begin(), v1.end() );

 
cout << "After, v2 is: ";

    for( vector<int>::size_type i = 0; i < v2.size(); i++ ) {
cout << v2[i] << " ";

    }

   cout << endl;

output :

    Before, v2 is: 5 6 7 8

    After, v2 is: 5 6 7 8 0 1 2 3

–删除（remove）元素

标准模板库(STL)学习指南之vector向量

eg.

    vector<char> alphas;

    for( int i=0; i < 10; i++ ) {

      static const char letters[] = "ABCDEFGHIJ";

      alphas.push_back( letters[i] );

    }

    vector<char>::size_type size = alphas.size();

    vector<char>::iterator startIterator;

    vector<char>::iterator tempIterator;

    for( vector<char>::size_type i=0; i < size; i++ ) {

      startIterator = alphas.begin();

      alphas.erase( startIterator );

      // Display the vector

      for( tempIterator = alphas.begin(); tempIterator != alphas.end(); ++tempIterator ) {
cout << *tempIterator;

      }
cout << endl;

    }

output:

    BCDEFGHIJ

    CDEFGHIJ

    DEFGHIJ

    EFGHIJ

    FGHIJ

    GHIJ

    HIJ

    IJ

    vector<char> alphas;

    for( int i=0; i < 10; i++ ) {

      static const char letters[] = "ABCDEFGHIJ";

      alphas.push_back( letters[i] );

    }

    // display the complete vector

    for( vector<char>::size_type i = 0; i < alphas.size(); i++ ) {
cout << alphas[i];

    }
cout << endl;

 

    // use erase to remove all but the first two and last three elements

    // of the vector

    alphas.erase( alphas.begin()+2, alphas.end()-3 );

    // display the modified vector

    for( vector<char>::size_type i = 0; i < alphas.size(); i++ ) {
cout << alphas[i];

    }

    cout << endl;

output:

    ABCDEFGHIJ

    ABHIJ

#include <iostream>

#include <vector>

#include <iterator>

 

using namespace std;

 

int main()

{

    vector<char> alphas;

    for( int i=0; i < 10; i++ ) {

      static const char letters[] = "ABCDEFGHIJ";

      alphas.push_back( letters[i] );

    }

 

    vector<char>::iterator iter = alphas.begin();

    while( iter != alphas.end() )

    {

      if (*iter == 'B' || *iter == 'D')

        iter = alphas.erase( iter );

      else

        ++iter;

    }

 

    copy(alphas.begin(), alphas.end(), ostream_iterator<char>(cout, ""));
cout << endl;

  }

output :

ACEFGHIJ

转载自：http://www.cppblog.com/MiYu/archive/2010/08/31/125459.html

作者：ACShiryu
出处：http://www.cnblogs.com/ACShiryu/
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