C++初阶vector(上)

Posted 2021-12-17 Huang_ZhenSheng

本文中的string类的常用接口可以查询相关的文档进行查看：文档查询

目录

1，vector的遍历

2，其他容器迭代器初始化，只要数据类型可以匹配上

3，rbegin  &  rend

4，reverse & resize

5，assign

6，insert 

7，sort

8，erase

---

1，vector的遍历

void test_vector1()

	vector<int>v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(3);
	v.push_back(4);
	v.push_back(5);
	//下标+[]
	for (size_t i = 0; i < v.size(); i++)
	
		//v[i] -= 1;
		cout << v[i] << " ";
	
	cout << endl;
	//迭代器
	vector<int>::iterator it = v.begin();
	while (it != v.end())
	
		*it += 1;
		cout << *it << " ";
		it++;
	
	cout << endl;
	//范围for
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;

int main()

	test_vector1();
	return 0;

2，其他容器迭代器初始化，只要数据类型可以匹配上

（*iterator 对象的类型跟vector中存的数据类型是一致的）

void test_vector2()

	string s("hello world");
	vector<char>v(s.begin(), s.end());
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;

3，rbegin  &  rend

vector<int>::reverse_iterator rit = v.rbegin();
	while (rit != v.rend())
	
		cout << *rit << " ";
		rit++;
	
	cout << endl;

4，reverse & resize

void test_vector4()

	vector<int>v;
	//cout << v.max_size() << endl;
	v.reserve(10);//开空间，改变容量
	//下面这样的用法是错误的——>operator[]中回去检查i是否小于size
	//for (size_t i = 0; i < 10; i++)
	//
	//	v[i] = i;//assert(i<_size)
	//
	for (size_t i = 0; i < 10; i++)
	
		v.push_back(i);
	
	v.resize(20, 1);//开空间+初始化
	for (size_t i = 0; i < 20; i++)
	
		v[i] = i;
	

5，assign

void test_vector5()

	int a[] =  1, 2, 3, 4, 5 ;
	vector<int>v;
	//[first,last)
	v.assign(a, a + 4);
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;

6，insert 

void test_vector6()

	int a[] =  1, 2, 3, 4, 5 ;
	vector<int>v(a, a + 5);
	//头插
	v.insert(v.begin(), 0);
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;

假设想在2的前面插入呢？

vector<int>::iterator pos = find(v.begin(), v.end(), 2);
	if (pos != v.end())
	
		v.insert(pos, 20);
	
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;

7，sort

//默认排升序
	sort(v.begin(), v.end());
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;
	//排降序—关于greater<int>是一个仿函数
	sort(v.begin(), v.end(), greater<int>());
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;

8，erase

//头删
	v.erase(v.begin());
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;
	//删除pos位置的数
	vector<int>::iterator pos = find(v.begin(), v.end(), 2);
	if (pos != v.end())
	
		v.erase(pos);
	
	for (auto e : v)
	
		cout << e << " ";
	
	cout << endl;