algorithm此头文件是算法库的一部分。本篇介绍修改序列的操作函数。

修改序列的操作
copycopy_if (C++11)	将某一范围的元素复制到一个新的位置 (函数模板)
copy_n (C++11)	将一定数目的元素复制到一个新的位置 (函数模板)
copy_backward	按从后往前的顺序复制一个范围内的元素 (函数模板)
move (C++11)	将某一范围的元素移动到一个新的位置 (函数模板)
move_backward (C++11)	按从后往前的顺序移动某一范围的元素到新的位置 (函数模板)
transform	将一个函数应用于某一范围的各个元素，并在目标范围存储结果 (函数模板)
replacereplace_if	将所有满足特定判别标准的值替换为另一个值 (函数模板)
replace_copyreplace_copy_if	复制一个范围，并将满足特定判别标准的元素替换为另一个值 (函数模板)
swap	交换两个对象的值 (函数模板)
swap_ranges	交换两个范围的元素 (函数模板)
iter_swap	交换两个迭代器所指向的元素 (函数模板)

示例代码

#include <algorithm>
#include <functional>
#include <iostream>
#include <iterator>
#include <utility>      // std::pair
#include <vector>
#include <array>
#include <cctype>       // std::tolower
#include <string>

int op_increase(int i) { return ++i; }

bool IsOdd12(int i) { return ((i % 2) == 1); }

int main()
{
	// copy algorithm example
	int myints1[] = { 10,20,30,40,50,60,70 };
	std::vector<int> myvector1(7);
	std::copy(myints1, myints1 + 7, myvector1.begin());
	std::cout << "myvector1 contains:";
	for (std::vector<int>::iterator it1 = myvector1.begin(); it1 != myvector1.end(); ++it1)
		std::cout << ' ' << *it1;
	std::cout << "\n";

	// copy_n algorithm example
	int myints2[] = { 10,20,30,40,50,60,70 };
	std::vector<int> myvector2;

	myvector2.resize(7);   // allocate space for 7 elements

	std::copy_n(myints2, 7, myvector2.begin());

	std::cout << "myvector2 contains:";
	for (std::vector<int>::iterator it2 = myvector2.begin(); it2 != myvector2.end(); ++it2)
		std::cout << ' ' << *it2;

	std::cout << "\n";

	// copy_if example
	std::vector<int> foo3 = { 25,15,5,-5,-15 };
	std::vector<int> bar3(foo3.size());
	// copy only positive numbers:
	auto it3 = std::copy_if(foo3.begin(), foo3.end(), bar3.begin(), [](int i) {return !(i < 0); });
	bar3.resize(std::distance(bar3.begin(), it3));  // shrink container to new size
	std::cout << "bar3 contains:";
	for (int& x : bar3) 
		std::cout << ' ' << x;
	std::cout << '\n';

	// copy_backward example
	std::vector<int> myvector4;
	// set some values:
	for (int i = 1; i <= 5; i++)
		myvector4.push_back(i * 10);          // myvector4: 10 20 30 40 50
	myvector4.resize(myvector4.size() + 3);  // allocate space for 3 more elements
	std::copy_backward(myvector4.begin(), myvector4.begin() + 5, myvector4.end());
	std::cout << "myvector4 contains:";
	for (std::vector<int>::iterator it4 = myvector4.begin(); it4 != myvector4.end(); ++it4)
		std::cout << ' ' << *it4;
	std::cout << '\n';

	// move algorithm example
	std::vector<std::string> foo5 = { "air","water","fire","earth" };
	std::vector<std::string> bar5(4);
	// moving ranges:
	std::cout << "Moving ranges...\n";
	std::move(foo5.begin(), foo5.begin() + 4, bar5.begin());
	std::cout << "foo5 contains " << foo5.size() << " elements:";
	std::cout << " (each in an unspecified but valid state)";
	std::cout << '\n';
	std::cout << "bar5 contains " << bar5.size() << " elements:";
	for (std::string& x : bar5) std::cout << " [" << x << "]";
	std::cout << '\n';
	// moving container:
	std::cout << "Moving container...\n";
	foo5 = std::move(bar5);
	std::cout << "foo5 contains " << foo5.size() << " elements:";
	for (std::string& x : foo5) std::cout << " [" << x << "]";
	std::cout << '\n';
	std::cout << "bar5 is in an unspecified but valid state";
	std::cout << '\n';

	// move_backward example
	std::string elems6[10] = { "air","water","fire","earth" };
	// insert new element at the beginning:
	std::move_backward(elems6, elems6 + 4, elems6 + 5);
	elems6[0] = "ether";
	std::cout << "elems6 contains:";
	for (int i = 0; i < 10; ++i)
		std::cout << " [" << elems6[i] << "]";
	std::cout << '\n';

	// swap algorithm example (C++98)
	int x7 = 10, y7 = 20;                              // x7:10 y7:20
	std::swap(x7, y7);                              // x7:20 y7:10
	std::vector<int> foo7(4, x7), bar7(6, y7);       // foo7:4x20 bar7:6x10
	std::swap(foo7, bar7);                          // foo7:6x10 bar7:4x20
	std::cout << "foo7 contains:";
	for (std::vector<int>::iterator it7 = foo7.begin(); it7 != foo7.end(); ++it7)
		std::cout << ' ' << *it7;
	std::cout << '\n';

	// swap_ranges example
	std::vector<int> foo8(5, 10);        // foo8: 10 10 10 10 10
	std::vector<int> bar8(5, 33);        // bar8: 33 33 33 33 33
	std::swap_ranges(foo8.begin() + 1, foo8.end() - 1, bar8.begin());
	// print out results of swap:
	std::cout << "foo8 contains:";
	for (std::vector<int>::iterator it8 = foo8.begin(); it8 != foo8.end(); ++it8)
		std::cout << ' ' << *it8;
	std::cout << '\n';
	std::cout << "bar8 contains:";
	for (std::vector<int>::iterator it8 = bar8.begin(); it8 != bar8.end(); ++it8)
		std::cout << ' ' << *it8;
	std::cout << '\n';

	// iter_swap example
	int myints9[] = { 10,20,30,40,50 };              //   myints9:  10  20  30  40  50
	std::vector<int> myvector9(4, 99);            // myvector9:  99  99  99  99
	std::iter_swap(myints9, myvector9.begin());     //   myints9: [99] 20  30  40  50
												 // myvector9: [10] 99  99  99
	std::iter_swap(myints9 + 3, myvector9.begin() + 2); //   myints9:  99  20  30 [99] 50
												 // myvector9:  10  99 [40] 99
	std::cout << "myvector9 contains:";
	for (std::vector<int>::iterator it9 = myvector9.begin(); it9 != myvector9.end(); ++it9)
		std::cout << ' ' << *it9;
	std::cout << '\n';

	// transform algorithm example
	std::vector<int> foo10;
	std::vector<int> bar10;
	// set some values:
	for (int i = 1; i < 6; i++)
		foo10.push_back(i * 10);                         // foo10: 10 20 30 40 50
	bar10.resize(foo10.size());                         // allocate space
	std::transform(foo10.begin(), foo10.end(), bar10.begin(), op_increase);
	// bar10: 11 21 31 41 51
	// std::plus adds together its two arguments:
	std::transform(foo10.begin(), foo10.end(), bar10.begin(), foo10.begin(), std::plus<int>());
	// foo: 21 41 61 81 101
	std::cout << "foo10 contains:";
	for (std::vector<int>::iterator it10 = foo10.begin(); it10 != foo10.end(); ++it10)
		std::cout << ' ' << *it10;
	std::cout << '\n';

	// replace algorithm example
	int myints11[] = { 10, 20, 30, 30, 20, 10, 10, 20 };
	std::vector<int> myvector11(myints11, myints11 + 8);            // 10 20 30 30 20 10 10 20
	std::replace(myvector11.begin(), myvector11.end(), 20, 99); // 10 99 30 30 99 10 10 99
	std::cout << "myvector11 contains:";
	for (std::vector<int>::iterator it11 = myvector11.begin(); it11 != myvector11.end(); ++it11)
		std::cout << ' ' << *it11;
	std::cout << '\n';

	// replace_if example
	std::vector<int> myvector12;
	// set some values:
	for (int i = 1; i < 10; i++) 
		myvector12.push_back(i);               // 1 2 3 4 5 6 7 8 9
	std::replace_if(myvector12.begin(), myvector12.end(), IsOdd12, 0); // 0 2 0 4 0 6 0 8 0
	std::cout << "myvector12 contains:";
	for (std::vector<int>::iterator it12 = myvector12.begin(); it12 != myvector12.end(); ++it12)
		std::cout << ' ' << *it12;
	std::cout << '\n';

	// replace_copy example
	int myints13[] = { 10, 20, 30, 30, 20, 10, 10, 20 };
	std::vector<int> myvector13(8);
	std::replace_copy(myints13, myints13 + 8, myvector13.begin(), 20, 99);
	std::cout << "myvector13 contains:";
	for (std::vector<int>::iterator it13 = myvector13.begin(); it13 != myvector13.end(); ++it13)
		std::cout << ' ' << *it13;
	std::cout << '\n';

	// replace_copy_if example
	std::vector<int> foo14, bar14;
	// set some values:
	for (int i = 1; i < 10; i++) 
		foo14.push_back(i);          // 1 2 3 4 5 6 7 8 9
	bar14.resize(foo14.size());   // allocate space
	std::replace_copy_if(foo14.begin(), foo14.end(), bar14.begin(), IsOdd12, 0);
	// 0 2 0 4 0 6 0 8 0
	std::cout << "bar14 contains:";
	for (std::vector<int>::iterator it14 = bar14.begin(); it14 != bar14.end(); ++it14)
		std::cout << ' ' << *it14;
	std::cout << '\n';



	std::cout << "hello world\n";
	return 0;
}

运行结果：

 参考：

https://cplusplus.com/reference/algorithm/

标准库标头 <algorithm> - cppreference.com