algorithm算法库学习之——修改序列的操作2

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。（2）

修改序列的操作
fill	将一个给定值复制赋值给一个范围内的每个元素 (函数模板)
fill_n	将一个给定值复制赋值给一个范围内的 N 个元素 (函数模板)
generate	将相继的函数调用结果赋值给一个范围中的每个元素 (函数模板)
generate_n	将相继的函数调用结果赋值给一个范围中的 N 个元素 (函数模板)
removeremove_if	移除满足特定判别标准的元素 (函数模板)
remove_copyremove_copy_if	复制一个范围的元素，忽略满足特定判别标准的元素 (函数模板)
reverse	逆转范围中的元素顺序 (函数模板)
reverse_copy	创建一个范围的逆向副本 (函数模板)
rotate	旋转范围中的元素顺序 (函数模板)
rotate_copy	复制并旋转元素范围 (函数模板)
random_shuffleshuffle (C++17 前)(C++11)	随机重排范围中的元素 (函数模板)
sample (C++17)	从一个序列中随机选择 N 个元素 (函数模板)
unique	移除范围内的连续重复元素 (函数模板)
unique_copy	创建某范围的不含连续重复元素的副本 (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>
#include <ctime>        // std::time
#include <cstdlib>      // std::rand, std::srand
#include <random>       // std::default_random_engine
#include <chrono>       // std::chrono::system_clock

// function generator:
int RandomNumber() { return (std::rand() % 100); }

// class generator:
struct c_unique {
	int current;
	c_unique() { current = 0; }
	int operator()() { return ++current; }
} UniqueNumber;

int current = 0;
int UniqueNumber2() { return ++current; }

bool IsOdd4(int i) { return ((i % 2) == 1); }

bool myfunction9(int i, int j) {
	return (i == j);
}

int myrandom(int i) { return std::rand() % i; }

int main()
{
	// fill algorithm example
	std::vector<int> myvector(8);                       // myvector: 0 0 0 0 0 0 0 0
	std::fill(myvector.begin(), myvector.begin() + 4, 5);   // myvector: 5 5 5 5 0 0 0 0
	std::fill(myvector.begin() + 3, myvector.end() - 2, 8);   // myvector: 5 5 5 8 8 8 0 0
	std::cout << "myvector contains:";
	for (std::vector<int>::iterator it = myvector.begin(); it != myvector.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	// fill_n example
	std::vector<int> myvector2(8, 10);        // myvector2: 10 10 10 10 10 10 10 10
	std::fill_n(myvector2.begin(), 4, 20);     // myvector2: 20 20 20 20 10 10 10 10
	std::fill_n(myvector2.begin() + 3, 3, 33);   // myvector2: 20 20 20 33 33 33 10 10
	std::cout << "myvector2 contains:";
	for (std::vector<int>::iterator it = myvector2.begin(); it != myvector2.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	// generate algorithm example
	std::srand(unsigned(std::time(0)));
	std::vector<int> myvector3(8);
	std::generate(myvector3.begin(), myvector3.end(), RandomNumber);
	std::cout << "myvector3 contains:";
	for (std::vector<int>::iterator it = myvector3.begin(); it != myvector3.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';
	std::generate(myvector3.begin(), myvector3.end(), UniqueNumber);
	std::cout << "myvector3 contains:";
	for (std::vector<int>::iterator it = myvector3.begin(); it != myvector3.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//generate_n  example
	int myarray[9];
	std::generate_n(myarray, 9, UniqueNumber2);
	std::cout << "myarray contains:";
	for (int i = 0; i < 9; ++i)
		std::cout << ' ' << myarray[i];
	std::cout << '\n';

	//remove  example
	int myints[] = { 10,20,30,30,20,10,10,20 };      // 10 20 30 30 20 10 10 20
	// bounds of range:
	int* pbegin = myints;                          // ^
	int* pend = myints + sizeof(myints) / sizeof(int); // ^                       ^
	pend = std::remove(pbegin, pend, 20);         // 10 30 30 10 10 ?  ?  ?
												  // ^              ^
	std::cout << "range contains:";
	for (int* p = pbegin; p != pend; ++p)
		std::cout << ' ' << *p;
	std::cout << '\n';

	//remove_if  example
	int myints5[] = { 1,2,3,4,5,6,7,8,9 };            // 1 2 3 4 5 6 7 8 9
	// bounds of range:
	int* pbegin5 = myints5;                          // ^
	int* pend5 = myints5 + sizeof(myints5) / sizeof(int); // ^                 ^
	pend5 = std::remove_if(pbegin5, pend5, IsOdd4);   // 2 4 6 8 ? ? ? ? ?
												   // ^       ^
	std::cout << "the range contains:";
	for (int* p = pbegin5; p != pend5; ++p)
		std::cout << ' ' << *p;
	std::cout << '\n';

	//remove_copy  example
	int myints6[] = { 10,20,30,30,20,10,10,20 };               // 10 20 30 30 20 10 10 20
	std::vector<int> myvector6(8);
	std::remove_copy(myints6, myints6 + 8, myvector6.begin(), 20); // 10 30 30 10 10 0 0 0
	std::cout << "myvector6 contains:";
	for (std::vector<int>::iterator it = myvector6.begin(); it != myvector6.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//remove_copy_if  example
	int myints7[] = { 1,2,3,4,5,6,7,8,9 };
	std::vector<int> myvector7(9);
	std::remove_copy_if(myints7, myints7 + 9, myvector7.begin(), IsOdd4);
	std::cout << "myvector7 contains:";
	for (std::vector<int>::iterator it = myvector7.begin(); it != myvector7.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//unique  example
	int myints8[] = { 10,20,20,20,30,30,20,20,10 };           // 10 20 20 20 30 30 20 20 10
	std::vector<int> myvector8(myints8, myints8 + 9);
	// using default comparison:
	std::vector<int>::iterator it8;
	it8 = std::unique(myvector8.begin(), myvector8.end());   // 10 20 30 20 10 ?  ?  ?  ?
														   //                ^
	myvector8.resize(std::distance(myvector8.begin(), it8)); // 10 20 30 20 10
	// using predicate comparison:
	std::unique(myvector8.begin(), myvector8.end(), myfunction9);   // (no changes)
	// print out content:
	std::cout << "myvector8 contains:";
	for (it8 = myvector8.begin(); it8 != myvector8.end(); ++it8)
		std::cout << ' ' << *it8;
	std::cout << '\n';

	//unique_copy  example
	int myints9[] = { 10,20,20,20,30,30,20,20,10 };
	std::vector<int> myvector9(9);                            // 0  0  0  0  0  0  0  0  0
	// using default comparison:
	std::vector<int>::iterator it9;
	it9 = std::unique_copy(myints9, myints9 + 9, myvector9.begin());   // 10 20 30 20 10 0  0  0  0
															  //                ^
	std::sort(myvector9.begin(), it9);                          // 10 10 20 20 30 0  0  0  0
															  //                ^
	// using predicate comparison:
	it9 = std::unique_copy(myvector9.begin(), it9, myvector9.begin(), myfunction9);
	// 10 20 30 20 30 0  0  0  0
	//          ^
	myvector9.resize(std::distance(myvector9.begin(), it9));    // 10 20 30
	// print out content:
	std::cout << "myvector9 contains:";
	for (it9 = myvector9.begin(); it9 != myvector9.end(); ++it9)
		std::cout << ' ' << *it9;
	std::cout << '\n';

	//reverse  example
	std::vector<int> myvector10;
	// set some values:
	for (int i = 1; i < 10; ++i) myvector10.push_back(i);   // 1 2 3 4 5 6 7 8 9
	std::reverse(myvector10.begin(), myvector10.end());    // 9 8 7 6 5 4 3 2 1
	// print out content:
	std::cout << "myvector10 contains:";
	for (std::vector<int>::iterator it = myvector10.begin(); it != myvector10.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//reverse_copy  example
	int myints11[] = { 1,2,3,4,5,6,7,8,9 };
	std::vector<int> myvector11;
	myvector11.resize(9);    // allocate space
	std::reverse_copy(myints11, myints11 + 9, myvector11.begin());
	// print out content:
	std::cout << "myvector11 contains:";
	for (std::vector<int>::iterator it = myvector11.begin(); it != myvector11.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//rotate  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::rotate(myvector12.begin(), myvector12.begin() + 3, myvector12.end());
	// 4 5 6 7 8 9 1 2 3
	// print out content:
	std::cout << "myvector12 contains:";
	for (std::vector<int>::iterator it = myvector12.begin(); it != myvector12.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//rotate_copy  example
	int myints13[] = { 10,20,30,40,50,60,70 };
	std::vector<int> myvector13(7);
	std::rotate_copy(myints13, myints13 + 3, myints13 + 7, myvector13.begin());
	// print out content:
	std::cout << "myvector13 contains:";
	for (std::vector<int>::iterator it = myvector13.begin(); it != myvector13.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//random_shuffle  example
	std::srand(unsigned(std::time(0)));
	std::vector<int> myvector14;
	// set some values:
	for (int i = 1; i < 10; ++i) myvector14.push_back(i); // 1 2 3 4 5 6 7 8 9
	// using built-in random generator:
	std::random_shuffle(myvector14.begin(), myvector14.end());
	// using myrandom:
	std::random_shuffle(myvector14.begin(), myvector14.end(), myrandom);
	// print out content:
	std::cout << "myvector14 contains:";
	for (std::vector<int>::iterator it = myvector14.begin(); it != myvector14.end(); ++it)
		std::cout << ' ' << *it;
	std::cout << '\n';

	//shuffle
	std::array<int, 5> foo15{ 1,2,3,4,5 };
	// obtain a time-based seed:
	unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
	shuffle(foo15.begin(), foo15.end(), std::default_random_engine(seed));
	std::cout << "shuffled elements:";
	for (int& x : foo15) std::cout << ' ' << x;
	std::cout << '\n';

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

运行结果：