vector容器主要的操作

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;


void printVector(vector<int>& v)
{
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

//初始化
void test01()
{
	vector<int> v1; //默认构造

	int arr[] = { 10, 20, 30, 40 };
	vector<int> v2(arr, arr + sizeof(arr) / sizeof(int));
	vector<int> v3(v2.begin(), v2.end());
	vector<int> v4(v3);

	printVector(v2);
	printVector(v3);
	printVector(v4);
	
}

//常用赋值操作
void test02()
{
	int arr[] = { 10, 20, 30, 40 };
	vector<int> v1(arr, arr + sizeof(arr) / sizeof(int));

	vector<int> v2;
	v2.assign(v1.begin(), v1.end());

	vector<int> v3;
	v3 = v2;

	int arr1[] = { 100, 200, 300, 400 };
	vector<int> v4(arr1, arr1 + sizeof(arr1) / sizeof(int));


	printVector(v1);
	printVector(v2);
	printVector(v3);
	printVector(v4);

	cout << "----------------" << endl;

	v4.swap(v1);
	printVector(v1);
	printVector(v2);
	printVector(v3);
	printVector(v4);

}

//大小操作
void test03()
{
	int arr1[] = { 100, 200, 300, 400 };
	vector<int> v4(arr1, arr1 + sizeof(arr1) / sizeof(int));
	
	cout << "size = " << v4.size() << endl;
	if (v4.empty())
	{
		cout << "空！" << endl;
	}
	else
	{
		cout << "不空！" << endl;
	}

	printVector(v4);
	v4.resize(2);
	printVector(v4);
	//v4.resize(6);
	//printVector(v4);
	v4.resize(6, 1);
	printVector(v4);

	for (int i = 0; i < 10000; i++)
	{
		v4.push_back(i);
	}

	cout << "size = " << v4.size() << endl; //元素个数
	cout << v4.capacity() << endl; //容量

}

//存取数据
void test04()
{
	int arr1[] = { 100, 200, 300, 400 };
	vector<int> v4(arr1, arr1 + sizeof(arr1) / sizeof(int));

	for (int i = 0; i < v4.size(); i++)
	{
		cout << v4[i] << " ";
	}
	cout << endl;

	for (int i = 0; i < v4.size(); i++)
	{
		cout << v4.at(i) << " ";
	}
	cout << endl;
	
	//区别： at抛异常 []不抛异常


	//返回第一个和最后一个元素
	cout << "front = " << v4.front() << endl;
	cout << "back = " << v4.back() << endl;

}

//插入和删除
void test05()
{
	vector<int> v;
	v.push_back(10);
	v.push_back(20);
	//头插法
	v.insert(v.begin(), 30);
	v.insert(v.end(), 40);

	v.insert(v.begin() + 2, 100); //vector支持随机访问


	//支持数组下标，一般都支持随机访问
	//迭代器可以直接+2 +3 -2 -5 操作
	printVector(v);

	//删除
	v.erase(v.begin());
	printVector(v);
	v.erase(v.begin() + 1, v.end());
	printVector(v);
	v.clear();
	cout << "size = " << v.size() << endl;

}

//巧用swap缩减空间
void test06()
{
	//vector添加元素 他会自动增长 你删除元素 他不会自动减少

	vector<int> v;
	for (int i = 0; i < 100000; i++)
	{
		v.push_back(i);
	}
	cout << "size = " << v.size() << endl;
	cout << "capacity = " << v.capacity() << endl;

	v.resize(10);
	cout << "---------------------------" << endl;
	cout << "size = " << v.size() << endl;
	cout << "capacity = " << v.capacity() << endl;

	//收缩空间
	vector<int>(v).swap(v);

	cout << "---------------------------" << endl;
	cout << "size = " << v.size() << endl;
	cout << "capacity = " << v.capacity() << endl;


}


void test07()
{
	//reserve预留空间 resize 区别
	int num = 0;
	int* address = NULL;

	vector<int> v;
	v.reserve(100000);
	for (int i = 0; i < 100000; i++)
	{
		v.push_back(i);
		if (address != &(v[0]))
		{
			address = &(v[0]);
			num++;
		}
	}

	cout << "num = " << num << endl;

	//如果你知道容器大概要存储的元素个数，那么你可以用reserve预留空间


}

int main()
{
	//test01();
	//test02();
	//test03();
	//test04();
	//test05();
	//test06();
	test07();


	return 0;
}