STL algorithm算法copy(6)

原文位址：http://www.cplusplus.com/reference/algorithm/copy/ function template <algorithm>

std::copy

template <class InputIterator, class OutputIterator>
  OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result);      

Copy range of elements Copies the elements in the range 

[first,last)

 into the range beginning at result.

複制範圍[first,last）裡面的元素到result的位置。（将會覆寫原來的資料）

例子：

#include <iostream>
#include <algorithm>
#include <vector>
#include <array>
using namespace std;
void copy1(){
    vector<int> v1{1,5,7,8,9};
    vector<int> v2{100,200,300};
    array<int,7> ai{888,666.555,222,111,555,777};
    vector<double> vd{9.9,8.8,7.7,};

    cout<<"at first,v1=";
    for(int &i:v1)
        cout<<i<<" ";
    cout<<endl;

    cout<<"at first,v2=";
    for(int &i:v2)
        cout<<i<<" ";
    cout<<endl;

    auto it=copy(v2.begin(),v2.end(),v1.begin());
    cout<<"after copy(v2.begin(),v2.end(),v1.begin())"<<endl;
    cout<<"v1=";
    for(int &i:v1)
        cout<<i<<" ";
    cout<<endl;

     cout<<"v2=";
    for(int &i:v2)
        cout<<i<<" ";
    cout<<endl;
    cout<<"the return it is :*it="<<*it<<endl;



}
           

運作截圖：

The function returns an iterator to the end of the destination range (which points to the element following the last element copied).

該函數傳回一個疊代器，指向目标範圍的最後（即last的下一個元素）（上面例子的8）

The ranges shall not overlap in such a way that result points to an element in the range [first,last). For such cases, see copy_backward.

result不應該指向[first,last)中的任一進制素，如果需要，應該使用copy_backward.（這句話很有問題，因為copy_backward也有一句幾乎一樣的話，具體需求請具體分析）

例子：

#include <iostream>
#include <algorithm>
#include <vector>
#include <array>
using namespace std;
void copy2(){
    vector<int> v1{1,5,7,8,9};

    cout<<"at first,v1=";
    for(int &i:v1)
        cout<<i<<" ";
    cout<<endl;


    auto it=copy(v1.begin(),v1.end(),v1.begin()+3);
    cout<<"after copy(v1.begin(),v1.end(),v1.begin()+3)"<<endl;
    cout<<"v1=";
    for(int &i:v1)
        cout<<i<<" ";
    cout<<endl;
    cout<<"the return it is :*it="<<*it<<endl;



}
           

運作截圖：

The behavior of this function template is equivalent to:

1 2 3 4 5 6 7 8 9

template<class InputIterator, class OutputIterator> OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result) { while (first!=last) { *result = *first; ++result; ++first; } return result; }

Parameters

first, last

Input iterators to the initial and final positions in a sequence to be copied. The range used is 

[first,last)

, which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.

要複制的範圍。

result

Output iterator to the initial position in the destination sequence.

This shall not point to any element in the range 

[first,last)

.

要覆寫資料的開頭。

不應該是[first,last)裡的任一進制素。

Return value

An iterator to the end of the destination range where elements have been copied.

傳回一個指向目标範圍最後一個元素的疊代器。

Example

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

// copy algorithm example #include <iostream> // std::cout #include <algorithm> // std::copy #include <vector> // std::vector int main () { int myints[]={10,20,30,40,50,60,70}; std::vector<int> myvector (7); std::copy ( myints, myints+7, myvector.begin() ); std::cout << "myvector contains:"; for (std::vector<int>::iterator it = myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }

Edit & Run

Output:

myvector contains: 10 20 30 40 50 60 70

Complexity

Linear in the distance between first and last: Performs an assignment operation for each element in the range.

Data races

The objects in the range 

[first,last)

 are accessed (each object is accessed exactly once).

The objects in the range between result and the returned value are modified (each object is modified exactly once).

result以及傳回值之間的所有元素都将會被修改。

Exceptions

Throws if either an element assignment or an operation on iterators throws.

Note that invalid arguments cause undefined behavior.

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//寫的錯誤或者不好的地方請多多指導，可以在下面留言或者點選左上方郵件位址給我發郵件，指出我的錯誤以及不足，以便我修改，更好的分享給大家，謝謝。

轉載請注明出處：http://blog.csdn.net/qq844352155

author:天下無雙

Email:[email protected]

2014-9-8

于GDUT

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