stl中copy()函數

C ++ STL std :: copy_if()函數 (C++ STL std::copy_if() function)

copy_if() function is a library function of algorithm header, it is used to copy the elements of a container, it copies the certain elements (which satisfy the given condition) of a container from the given start position to another container from the given beginning position.

copy_if()函數是算法標頭的庫函數，用于復制容器的元素，它將容器的某些元素(滿足給定條件)從給定的開始位置復制到另一個容器，從給定的開始位置位置。

Note:To use copy_if() function – include <algorithm> header or you can simple use <bits/stdc++.h> header file.

注意：要使用copy_if()函數 –包括<algorithm>頭文件，或者您可以簡單地使用<bits / stdc ++。h>頭文件。

Syntax of std::copy_if() function

std :: copy_if()函數的語法

std::copy_n(iterator source_first, iterator source_end, iterator target_start, UnaryPredicate pred);

Parameter(s):

參數：

• iterator source_first, iterator source_end – are the iterator positions of the source container.

  迭代器source_first，迭代器source_end –是源容器的迭代器位置。

• iterator target_start – is the beginning iterator of the target container.

  迭代器target_start –是目標容器的開始迭代器。

• UnaryPredicate pred – Unary function which accepts an element in the range as an argument, and returns a value convertible to bool.

  UnaryPredicate pred –一元函數，該函數接受范圍內的元素作為參數，并返回可轉換為bool的值。

Return value: iterator – it is an iterator to the end of the target range where elements have been copied.

返回值： 迭代器 –它是目標元素已復制到目標范圍末尾的迭代器。

Example:

例：

Input://declaring & initializing an int arrayint arr[] = { 10, 20, 30, 40, 50 };//vector declarationvector<int> v1(5);//copying 5 array elements to the vectorcopy_n(arr, 5, v1.begin());Output://if we print the valuearr: 10 20 30 40 50v1: 10 20 30 40 50

C ++ STL程序演示std :: copy_if()函數的使用 (C++ STL program to demonstrate use of std::copy_if() function)

In this example, we are copying only positive elements of the array to the vector.

在此示例中，我們僅將數組的正元素復制到向量。

//C++ STL program to demonstrate use of //std::copy_if() function #include <iostream> #include <algorithm> #include <vector> using namespace std;int main() {//declaring & initializing an int arrayint arr[] = { 10, 20, 30, -10, -20, 40, 50 };//vector declarationvector<int> v1(7);//copying 5 array elements to the vectorcopy_if(arr, arr + 7, v1.begin(), [](int i) { return (i >= 0); });//printing arraycout << "arr: ";for (int x : arr)cout << x << " ";cout << endl;//printing vectorcout << "v1: ";for (int x : v1)cout << x << " ";cout << endl;return 0; }

Output

輸出量

arr: 10 20 30 -10 -20 40 50 v1: 10 20 30 40 50 0 0

Reference: C++ std::copy_if()

參考： C ++ std :: copy_if()

翻譯自: https://www.includehelp.com/stl/std-copy_if-function-with-example.aspx

stl中copy()函數

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