C++でベクトルをコピーする方法

C++でベクトルをコピーする方法はいくつかあります。

1）std ::copy

std ::copyは、あるベクトルから別のベクトルに要素をコピーするために組み込まれています。

構文

std::copy(first_iterator_o, last_iterator_o, back_inserter()):
first_iteratot_0 = First iterator of first vector.
last_iteratot_0 = Last iterator of first vector.
back_inserter() = To insert values from back.

アルゴリズム

Begin
   Declare v1 of vector type.
      Initialize some values into v1 vector in array pattern.
   Declare v2 of vector type.
   Call copy(v1.begin(), v1.end(), back_inserter(v2)) to copy all
   elements of v1 to v2.
   Print “v1 vector elements are :”.
   for (int i=0;i<1.size; i++)
      print the all element of v2 vector.
   Print “v2 vector elements are :”.
   for (int i=0;i<2.size; i++)
      print the all element of v2 vector.
End.

サンプルコード

#include<iostream>
#include<vector>
#include<algorithm> // for copy.
#include<iterator> // for back_inserter
using namespace std;
int main() {
   vector<int> v1{ 7, 6, 4, 5 };
   vector<int> v2;
   copy(v1.begin(), v1.end(), back_inserter(v2));
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

出力

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5

2）演算子の割り当て

これは、ベクトル1からベクトル2に値をコピーするためにも使用されます。

構文

std::assign(first_iterator_o, last_iterator_o):
first_iteratot_0 = First iterator of first vector.
last_iteratot_0 = Last iterator of first vector.

アルゴリズム

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2.
   Call assign() to copy the elements of v1 to v2.
   Print the elements of v1.
   Print the elements of v2.
End.

サンプルコード

#include<iostream> #include<vector> // for vector #include<iostream>
#include<vector>// for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2;
   v2.assign(v1.begin(), v1.end());
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

出力

v1 vector elements are : 7 6 4 5 v2 vector elements are : 7 6 4 5

3）代入「=」演算子による

ベクトル1からベクトル2に値をコピーする簡単な方法です

アルゴリズム

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2.
   Call assignment operator “=” to copy the elements of v1 to v2.
   Print the elements of v1.
   Print the elements of v2.
End.

サンプルコード

#include<iostream>
#include<vector> // for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2;
   v2 = v1 ;
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

出力

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5

4）push_backメソッドによる

アルゴリズム

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2.
   Make a for loop to copy elements of first vector into second vector by Iterative method using push_back().
   Print the elements of v1.
   Print the elements of v2.
End.

サンプルコード

#include<iostream> #include<vector> // for vector
#include<iostream>
#include<vector>// for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2;
   for (int i=0; i<v1.size(); i++)
      v2.push_back(v1[i]);
      cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

出力

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5

5）コンストラクターとしてベクトルを渡すことによって

アルゴリズム

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2 and copying elements of first vector to second vector using constructor method and they are deeply copied.
   Print the elements of v1.
   Print the elements of v2.
End.

サンプルコード

#include<iostream>
#include<vector>// for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2(v1);
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

出力

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5