C++学习日志32------Vector容器、结构化绑定

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一、Vector容器

Vector容器是一个长度可变的数组(称为向量)。

#pragma once
#include<vector>
#include<iostream>
#include<string>
#define PRINT(x) std::cout<<#x<<":"<<x<<std::endl;

template<typename T>
std::ostream& operator<<(std::ostream& s, const std::vector<T>& v)
{
    
    
	s.put('[');
	char comma[3] = {
    
     '\0',' ','\0' };
	for (const auto& e : v)
	{
    
    
		s << comma << e;
		comma[0] = ',';
	}
	return s << ']';
}

int main()
{
    
    
	//用C++11的列表初始化 创建vector对象words1
	std::vector<std::string> words1{
    
     "Hello","World","Welcome","To","C!" };
	PRINT(words1);

	//删除words1最后一个元素
	words1.erase(words1.end() - 1);
	PRINT(words1);

	//在words1尾部追加元素
	words1.push_back("C++！");
	PRINT(words1);

	//用迭代器拷贝words1的内容以创建words2
	std::vector words2(words1.begin() + 2, words1.end());
	PRINT(words2);

	//在words2中插入元素
	words2.insert(words2.begin(), "Hello!");
	PRINT(words2);

	//用拷贝构造创建words3
	std::vector words3(words2);
	PRINT(words3);

	//用[]修改words3的元素
	words3[3] = "C Plus Plus";
	PRINT(words3);

	//创建words4,初始化为多个相同的字串
	std::vector<std::string> words4(4, "C++!");
	PRINT(words4);

	//words3与words4交换
	words3.swap(words4);
	PRINT(words3);
	PRINT(words4);

	std::cin.get();
}

结果如上图所示。

二、结构化绑定

结构化绑定可以理解为里面的元素顺序对应赋值。

#include<iostream>
#include<array>
//定义结构体，包含double和int成员
struct S
{
    
    
	//calss S{ public:
	double d1{
    
     1.0 };
	int i1{
    
     32 };

};
class C
{
    
    
public:
	int i2{
    
     1 };
	char c[3]{
    
     'a','b','\0' };
};

int main()
{
    
    

	std::array a{
    
     1,2,3 };
	std::array<int, 2> b{
    
     11,12 };
	auto& [e1, e2, e3] = a;

	a[0] = 10;

	std::cout << e1 << "  " << e2 << "  " << e3 << std::endl;

	//定义结构体和类对象 
	S s;
	C c;
	//绑定结构体变量
	auto [d1, i1] {
    
    s};
	//以引用形式绑定类对象成员
	auto& [i2, c2] {
    
    c};
	//输出绑定的成员

	std::cout << "s.d=" << d1 << "  s.i1=" << i1 << std::endl;
	std::cout << "c.i2= " << i2 << " c.c[3]= " << c2 << std::endl;
	std::cin.get();
	return 0;

}

结果如上图所示