STL_算法_06_遍历算法

◆ 常用的遍历算法：

1.1、用指定函数依次对指定范围内所有元素进行迭代访问。该函数不得修改序列中的元素

functor for_each(iteratorBegin, iteratorEnd, functor对每个元素进行操作);

1.2、与for_each类似，遍历所有元素，但可对容器的元素进行修改（ transform 是变换的意思）

OutputIterator transform(InputIterator _First1, InputIterator _Last1, OutputIterator _Result, 一元functor对每个元素进行操作);
OutputIterator transform(InputIterator1 _First1, InputIterator1 _Last1, InputIterator2 _First2, OutputIterator _Result, 二元functor对每个元素进行操作);

1、

1.1、第6讲 PPT.42

◆ for_each() : 用指定函数依次对指定范围内所有元素进行迭代访问。该函数不得修改序列中的元素。

ZC: 只有一种参数格式，返回值为传入的functor 。

ZC: vs2010 测试代码：

#ifdef WIN32
#pragma warning (disable: 4786)
#endif

#include <string>
#include <vector>
#include <set>

#include <algorithm>    // 算法
#include <numeric>    // 算法
#include <functional>    // 算法

using namespace std;

typedef void (*FUNC1)(const int &_iItem);
void (*FUNC2)(const int &_iItem);

void Show(const int &iItem)
{
    //cout << iItem;
    printf("iItem : %d\n", iItem);
}

void main()
{
    int iArray[] = {0,1,2,3,4};
    vector<int> vecInt(iArray, iArray+sizeof(iArray)/sizeof(iArray[0]));
    //FUNC1 = for_each(vecInt.begin(), vecInt.end(), Show); // ZC: 编译通不过
    FUNC2 = for_each(vecInt.begin(), vecInt.end(), Show);

    if (FUNC2 == Show)
        printf("FUNC2 == Show\n");
    else
        printf("FUNC2 != Show\n");

    system("pause");
}

ZC：控制台输出：

iItem : 0
iItem : 1
iItem : 2
iItem : 3
iItem : 4
FUNC2 == Show
请按任意键继续. . .

1.2、第6讲 PPT.42

◆ transform() : 与for_each类似，遍历所有元素，但可对容器的元素进行修改

ZC: 2种参数格式，返回值为输出容器中经过转换后的最后一个元素的iterator 。

ZC: VC6 测试代码：

 1 #ifdef WIN32
 2 #pragma warning (disable: 4786)
 3 #endif
 4 
 5 #include <string>
 6 #include <vector>
 7 #include <set>
 8 
 9 #include <algorithm>    // 算法
10 #include <numeric>    // 算法
11 #include <functional>    // 算法
12 
13 using namespace std;
14 
15 int Increase (int i)  
16 {  
17     return i+1;   
18 }  
19 
20 void main()
21 {
22     vector<int> vecIntA;
23     vecIntA.push_back(1);
24     vecIntA.push_back(3);
25     vecIntA.push_back(5);
26     vecIntA.push_back(7);
27     vecIntA.push_back(9);
28 
29     transform(vecIntA.begin(), vecIntA.end(), vecIntA.begin(), Increase);    //vecIntA : {2,4,6,8,10}
30 
31     int iIdx = 0;
32     vector<int>::iterator it = vecIntA.begin();
33     while (it != vecIntA.end())
34     {
35         printf("[%02d] ==> %d\n", iIdx, *it);
36         it ++;
37     }
38 }

ZC：控制台输出 - 1：

1 [00] ==> 2
2 [00] ==> 4
3 [00] ==> 6
4 [00] ==> 8
5 [00] ==> 10
6 Press any key to continue

ZC: vs10 测试代码：

 1 // alg_transform.cpp
 2 // compile with: /EHsc
 3 #include <vector>
 4 #include <algorithm>
 5 #include <functional>
 6 #include <iostream>
 7 
 8 // The function object multiplies an element by a Factor
 9 template <class Type>
10 class MultValue
11 {
12    private:
13       Type Factor;   // The value to multiply by
14    public:
15       // Constructor initializes the value to multiply by
16       MultValue ( const Type& _Val ) : Factor ( _Val )
17       {}
18 
19       // The function call for the element to be multiplied
20       int operator ( ) ( Type& elem ) const 
21       {
22          return elem * Factor;
23       }
24 };
25 
26 template <class Type>
27 class MultValue2
28 {
29    private:
30       Type Factor;   // The value to multiply by
31    public:
32       // Constructor initializes the value to multiply by
33       MultValue2 ( const Type& _Val ) : Factor ( _Val )
34       {}
35 
36       // The function call for the element to be multiplied
37       int operator ( ) ( Type& elem1, Type& elem2 ) const 
38       {
39          return elem1*elem2 * Factor;
40       }
41 };
42 
43 int main( )
44 {
45    using namespace std;
46    vector <int> v1, v2(7), v3(7);
47    vector <int>::iterator Iter1, Iter2 , Iter3;
48 
49    // Constructing vector v1
50    int i;
51    for ( i = -4 ; i <= 2 ; i++ )
52    {
53       v1.push_back(  i );
54    }
55 
56    cout << "Original vector  v1 = ( " ;
57    for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
58       cout << *Iter1 << " ";
59    cout << ")." << endl << endl;
60 
61    // Modifying the vector v1 in place
62    transform (v1.begin ( ) , v1.end ( ) , v1.begin ( ) , MultValue<int> ( 2 ) );
63    cout << "The elements of the vector v1 multiplied by 2 in place gives:"
64         << "\n v1mod = ( " ;
65    for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
66       cout << *Iter1 << " ";
67    cout << ")." << endl << endl;
68 
69    // Using transform to multiply each element by a factor of 5
70    transform ( v1.begin ( ) , v1.end ( ) , v2.begin ( ) , MultValue<int> ( 5 ) );
71    
72    cout << "Multiplying the elements of the vector v1mod\n "
73         <<  "by the factor 5 & copying to v2 gives:\n v2 = ( " ;
74    for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
75       cout << *Iter2 << " ";
76    cout << ")." << endl << endl;
77 
78    // The second version of transform used to multiply the 
79    // elements of the vectors v1mod & v2 pairwise
80    // ZC: 预定义的 二元functor
81    //transform ( v1.begin ( ) , v1.end ( ) ,  v2.begin ( ) , v3.begin ( ) , 
82    //   multiplies <int> ( ) );
83    // ZC: 自定义的 二元functor
84    transform ( v1.begin ( ) , v1.end ( ) ,  v2.begin ( ) , v3.begin ( ) , MultValue2<int> ( 2 ) );
85    
86    
87    cout << "Multiplying elements of the vectors v1mod and v2 pairwise "
88         <<  "gives:\n v3 = ( " ;
89    for ( Iter3 = v3.begin( ) ; Iter3 != v3.end( ) ; Iter3++ )
90       cout << *Iter3 << " ";
91    cout << ")." << endl;
92 
93    system("pause");
94 }

ZC：控制台输出 - 2：

 1 Original vector  v1 = ( -4 -3 -2 -1 0 1 2 ).
 2 
 3 The elements of the vector v1 multiplied by 2 in place gives:
 4  v1mod = ( -8 -6 -4 -2 0 2 4 ).
 5 
 6 Multiplying the elements of the vector v1mod
 7  by the factor 5 & copying to v2 gives:
 8  v2 = ( -40 -30 -20 -10 0 10 20 ).
 9 
10 Multiplying elements of the vectors v1mod and v2 pairwise gives:
11  v3 = ( 640 360 160 40 0 40 160 ).
12 请按任意键继续. . .

?.?、第6讲 PPT.?

◆

ZC: VC6 测试代码：

ZC：控制台输出：

posted @ 2016-03-04 14:17 CppSkill 阅读(280) 评论(0) 收藏举报

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STL_算法_06_遍历算法

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