(转)C++ Vector的使用

c++ vector

Posted on 2007-10-23 21:04 把大海藏到心里 阅读(290) 评论(0) 编辑 收藏 所属分类: c/c++



一.语法:

#include <vector>

vector(); 默认构造函数

vector( const vector& c ); 从一个已知的vector对象复制到新vector对象中

vector( size_type num, const TYPE& val = TYPE() ); 有num个元素,如果有val,则每个元素的值都是val

vector( input_iterator start, input_iterator end ); 被初始化为start到end的元素

~vector(); 析钩函数

例子:

// create a vector of random integers   创建一个包含随机数的vector对象

cout <<"original vector: ";

vector<int> v;

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

int num =(int) rand()%10;

cout << num <<" ";

v.push_back( num );

}

cout << endl;

// find the first element of v that is even   找到vector对象中的第一个元素

vector<int>::iterator iter1 = v.begin();

while( iter1 != v.end()&&*iter1 %2!=0){

iter1++;

}

// find the last element of v that is even   找到最后一个元素

vector<int>::iterator iter2 = v.end();

do{

iter2--;

}while( iter2 != v.begin()&&*iter2 %2!=0);

// only proceed if we find both numbers   找到初始和结束的元素

if( iter1 != v.end()&& iter2 != v.begin()){

cout <<"first even number: "<<*iter1 <<", last even number: "<<*iter2 << endl;

cout <<"new vector: ";

vector<int> v2( iter1, iter2 );

for(int i =0; i < v2.size(); i++){

cout << v2[i]<<" ";

}

cout << endl;

}

结果:

original vector:1979272198

first even number:2, last even number:8

new vector:27219

二:方法

1.assign

#include <vector>

void assign( size_type num, const TYPE& val );

void assign( input_iterator start, input_iterator end );

例子:

[code]vector<int> v;

v.assign(10,42); 构造函数1

for(int i =0; i < v.size(); i++){

cout << v[i]<<" ";

}

cout << endl;

结果:42424242424242424242

vector<int> v1;

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

v1.push_back( i );

}

vector<int> v2;

v2.assign( v1.begin(), v1.end());   构造函数2

for(int i =0; i < v2.size(); i++){

cout << v2[i]<<" ";

}

cout << endl;

结果：0123456789

2.at

#include <vector>

TYPE& at( size_type loc );

const TYPE& at( size_type loc ) const;

例子:

vector<int> v(5,1);

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

cout <<"Element "<< i <<" is "<< v[i]<< endl;

}

下面的安全些:

vector<int> v(5,1);

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

cout <<"Element "<< i <<" is "<< v.at(i)<< endl;

}

3.back

#include <vector>

TYPE& back();

const TYPE& back() const;

例子:

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;

结果:

The first element is0and the last element is4

4.begin

#include <vector>

iterator begin();

const_iterator begin() const;

例子:

vector<string> words;

string str;

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

vector<string>::iterator iter;

for( iter = words.begin(); iter != words.end(); iter++){

cout <<*iter << endl;

}

结果：

输入:hey mickey you're so fine

输出:hey

mickey

you're

so

fine

5.capacity

#include <vector>

size_type capacity() const;

例子:

vector<int> v1(10);

cout <<"The capacity of v1 is "<< v1.capacity()<< endl;

vector<int> v2;

v2.reserve(20);

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

结果:

The capacity of v1 is10

The capacity of v2 is20

6.clear

#include <vector>

void clear();

清空所有元素[/code]