STL学习笔记----7.STL迭代器

 

STL迭代器
一. 迭代器类型

Input迭代器                        istream

Output迭代器                     ostream

Forward迭代器

Bidirectional迭代器          list, set, multiset, map,multimap

Random access迭代器   vector, deque, string, array

注：随机迭代器，提供”迭代器算术运算”，比如：

Iter
索引位置为n的元素

Iter+=n向前跳n个元素

Iter-=n  向后跳n个元素

Iter1 < iter2 判断iter1是否在iter2之前

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for (int i=0;i<coll.size(); ++i) { 

   cout << coll.begin() [i]<< ' '; 
// iter
 
} 
 
for (pos =coll.begin(); pos < coll.end()-1; pos += 2) { 
//注意，只有随机迭代器才能用 operator <  
   cout << *pos << ' ';  
} 

for (int i=0;i<coll.size(); ++i) {
cout << coll.begin() [i]<< ' ';  // iter

}

for (pos =coll.begin(); pos < coll.end()-1; pos += 2) {  //注意，只有随机迭代器才能用 operator <
cout << *pos << ' ';
}

二. 迭代器相关辅助函数

1. advance()， 可将迭代器的位置增加或减少，增加的幅度由参数决定。

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#include <iterator> 

void advance (InputIterator& pos, Dist n) 

#include <iterator>
void advance (InputIterator& pos, Dist n)

注：n可以是负值，advance()不检查迭代器是否超过序列end()

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#include <iostream> 

#include <list> 
#include <algorithm> 

using namespace std; 

 
int main() 
{ 
       list<int> coll; 
 
       //insert elements from 1 to 9 

       for (int i=1; i<=9; ++i) { 

            coll.push_back(i); 
       } 
 
       list<int>::iterator pos = coll.begin(); 

 
       //print actual element 

       cout << *pos << endl;  // 1 

 
       //step three elements forward 

       advance (pos, 3); 
 
       //print actual element 

       cout << *pos << endl; // 4 

 
       //step three elements backward 

       advance (pos, -1); 
 
       //print actual element 

       cout << *pos << endl; // 3 

} 

#include <iostream>
#include <list>
#include <algorithm>
using namespace std;

int main()
{
list<int> coll;

//insert elements from 1 to 9
for (int i=1; i<=9; ++i) {
coll.push_back(i);
}

list<int>::iterator pos = coll.begin();

//print actual element
cout << *pos << endl;  // 1

//step three elements forward
advance (pos, 3);

//print actual element
cout << *pos << endl; // 4

//step three elements backward
advance (pos, -1);

//print actual element
cout << *pos << endl; // 3
}

2. distance()，用来处理两个迭代器之间的距离。

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#include <iterator> 

Dist distance (InputIterator pos1, InputIterator pos2) 

#include <iterator>
Dist distance (InputIterator pos1, InputIterator pos2)

注：两个迭代器必须指向同一个容器，如果不是随机迭代器，则pos2的位置必须与pos1相同或在其后。

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#include <iostream> 

#include <list> 
#include <algorithm> 

using namespace std; 

 
int main() 
{ 
       list<int> coll; 
 
       //insert elements from -3 to 9 

       for (int i=-3; i<=9; ++i) { 

           coll.push_back(i);  
       } 
 
       //search element with value 5 

       list<int>::iterator pos; 

       pos = find (coll.begin(), coll.end(),       
//range 
                   5);                             
//value 
 
       if (pos != coll.end()) { 

           //process and print difference from the beginning 

           cout << "difference between beginning and 5: " 

                << distance(coll.begin(),pos) << endl;
//8, 第一个位置的distance是0 
       } 
       else { 
            cout << "5 not found" << endl;  

       }  
} 

#include <iostream>
#include <list>
#include <algorithm>
using namespace std;

int main()
{
list<int> coll;

//insert elements from -3 to 9
for (int i=-3; i<=9; ++i) {
coll.push_back(i);
}

//search element with value 5
list<int>::iterator pos;
pos = find (coll.begin(), coll.end(),        //range
5);                              //value

if (pos != coll.end()) {
//process and print difference from the beginning
cout << "difference between beginning and 5: "
<< distance(coll.begin(),pos) << endl; //8, 第一个位置的distance是0
}
else {
cout << "5 not found" << endl;
}
}

3. iter_swap()， 可交换两个迭代器所指的内容。

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#include <algorithm> 

void iter_swap (ForwardIterator1 pos1, ForwardIterator2 pos2) 

#include <algorithm>
void iter_swap (ForwardIterator1 pos1, ForwardIterator2 pos2)

注：交换迭代器pos1和pos2所指的值，迭代器类型不必相同，但其中所指的值必须可以相互赋值。

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#include <iostream> 

#include <list> 
#include <algorithm> 

#include "print.hpp" 
using namespace std; 

 
int main()  
{ 
       list<int> coll; 

 
       //insert elements from 1 to 9 

       for (int i=1; i<=9; ++i) { 

           coll.push_back(i);  
       } 
 
       PRINT_ELEMENTS(coll);  // 1 2 3 4 5 6 7 8 9 

 
       //swap first and second value 

       iter_swap (coll.begin(), ++coll.begin()); 
 
 
       PRINT_ELEMENTS(coll);  // 2 1 3 4 5 6 7 8 9 

 
 
       //swap first and last value 

       iter_swap (coll.begin(), --coll.end()); 
 
       PRINT_ELEMENTS(coll);  // 9 1 3 4 5 6 7 8 2 

} 

#include <iostream>
#include <list>
#include <algorithm>
#include "print.hpp"
using namespace std;

int main()
{
list<int> coll;

//insert elements from 1 to 9
for (int i=1; i<=9; ++i) {
coll.push_back(i);
}

PRINT_ELEMENTS(coll);  // 1 2 3 4 5 6 7 8 9

//swap first and second value
iter_swap (coll.begin(), ++coll.begin());

PRINT_ELEMENTS(coll);  // 2 1 3 4 5 6 7 8 9

//swap first and last value
iter_swap (coll.begin(), --coll.end());

PRINT_ELEMENTS(coll);  // 9 1 3 4 5 6 7 8 2
}

三. 迭代器配接器

1. Reverse(逆向)迭代器

2. Insert(插入)迭代器

3. Stream(流)迭代器