【C++STL ：vector类 (一) 】详解vector类的使用层&&vector实践：算法题练习

void Print(const vector<int>& v)
{
	for (size_t i = 0; i < v.size(); i++)
	{
		cout << v[i] << " ";
	}
	cout << endl;
}

	//范围for
	for (auto e : v)
	{
		cout << e << " ";
	}
	cout << endl;

	vector<int>::const_iterator it = v.begin();
	while (it != v.end())
	{
		cout << "it" << " ";
		++it;
	}
	cout << endl;

// 测试vector的默认扩容机制
void TestVectorExpand()
{
	size_t sz;
	vector<int> v;
	sz = v.capacity();
	cout << "making v grow:\n";
	for (int i = 0; i < 100; ++i)
	{
		v.push_back(i);
		if (sz != v.capacity())
		{
			sz = v.capacity();
			cout << "capacity changed: " << sz << '\n';
		}
	}
}

making foo grow:
capacity changed: 1
capacity changed: 2
capacity changed: 3
capacity changed: 4
capacity changed: 6
capacity changed: 9
capacity changed: 13
capacity changed: 19
capacity changed: 28
capacity changed: 42
capacity changed: 63
capacity changed: 94
capacity changed: 141

making foo grow:
capacity changed: 1
capacity changed: 2
capacity changed: 4
capacity changed: 8
capacity changed: 16
capacity changed: 32
capacity changed: 64
capacity changed: 128

// 如果已经确定vector中要存储元素大概个数，可以提前将空间设置足够
// 就可以避免边插入边扩容导致效率低下的问题了
void TestVectorExpandOP()
{
	vector<int> v;
	size_t sz = v.capacity();
	v.reserve(100);   // 提前将容量设置好，可以避免一遍插入一遍扩容
	cout << "making bar grow:\n";
	for (int i = 0; i < 100; ++i)
	{
		v.push_back(i);
		if (sz != v.capacity())
		{
			sz = v.capacity();
			cout << "capacity changed: " << sz << '\n';
		}
	}
}

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int value = 0;
        for(auto e : nums)
        {
            //异或
            value ^= e;
            cout << endl;
        }
        return value;
    }
};

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> vv;
        //定义行
        vv.resize(numRows,vector<int>());
        //定义列
        for(size_t i = 0;i < numRows;++i)
        {
            vv[i].resize(i + 1,1);//1
        }

        for(size_t i = 2;i < vv.size();++i)//第0、1行的都不需要处理，1
        {
            for(size_t j = 1;j < vv[i].size() - 1;++j)
            {
                vv[i][j] = vv[i-1][j] + vv[i-1][j-1];
            }
        }
        return vv;
    }
};

#define  _CRT_SECURE_NO_WARNINGS  1
#include<iostream>
#include<vector>
using namespace std;

void Print(const vector<int>& v)
{
	for (size_t i = 0; i < v.size(); i++)
	{
		cout << v[i] << " ";
	}
	cout << endl;

	////范围for
	//for (auto e : v)
	//{
	//	cout << e << " ";
	//}
	//cout << endl;
	//
	//vector<int>::const_iterator it = v.begin();
	//while (it != v.end())
	//{
	//	cout << "it" << " ";
	//	++it;
	//}
	//cout << endl;
}

void Test_vector1()
{
	//构造
	vector<int> v1;//空
	vector<int>v2(10, 1);
	vector<int>v3(v2.begin(),v2.end());//迭代器
	string s1("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
	vector<int>v4(s1.begin(), s1.end());
	vector<int>v5(v3);

	//vector<int> v6({ 1,2,3,4,5,6 });
	vector<int> v6 = { 1,2,3,4,5,6 };
	vector<int> v7 = { 1,2,3,4,5,6,1,1,1,1,1,1 };

	Print(v2);
	Print(v4);
	Print(v6);
	Print(v7);

	auto il = { 10,20,30,1,2,2 };
	for (auto e : il)
	{
		cout << e << " ";
	}
	cout << endl;
}

void Test_vector2()
{
	vector<int> v1;
	//count int n = 1000000000000;
	const int n = 100;
	/*v1.reserve(n);*/

	size_t old = v1.capacity();
	/*cout << v1.capacity() << endl;*/
	size_t begin = clock();
	for (size_t i = 0; i < n; i++)
	{
		v1.push_back(i);

		if (old != v1.capacity())
		{
			cout << v1.capacity() << endl;
			old = v1.capacity();
		}
	}
	size_t end = clock();
	cout << end - begin << endl;

	vector<int> v2;
	v2.resize(100.1);
	Print(v2);
}

void Test_vector3()
{
	vector<int> v1 = { 1,2,3,4,5 };
	v1.push_back(6);
	Print(v1);

	v1.insert(v1.begin(), 0);
	Print(v1);

	v1.insert(v1.begin() + 3, 0);
	Print(v1);

	v1.erase(v1.begin());
	Print(v1);

	v1.erase(v1.begin() + 3);
	Print(v1);
}

//struct在C++里面也是类
struct AA
{
	int _a1 = 1;
	int _a2 = 1;

	AA(int a1 = 1,int a2 = 1)
		:_a1(a1)
		,_a2(a2)
	{ }
};

////模版
//template<class T>
//class vector
//{
//private:
//	T* _a;
//	size_t _size;
//	size_t _capacity;
//};

void Test_vector4()
{
	AA aa1 = { 0,0 };
	vector<AA> v = { aa1,{1,1},{2,2},{3,3} };
	auto it = v.begin();
	while (it != v.end())
	{
		cout << it->_a1 << ":" << it->_a2 << endl;
		++it;
	}
	cout << endl;

	//传AA对象
	v.push_back(aa1);
	v.emplace_back(aa1);

	//传构造AA对象的参数
	v.emplace_back(1, 1);
	v.push_back({ 2,2 });

	it = v.begin();
	while (it != v.end())
	{
		cout << it->_a1 << ":" << it->_a2 << endl;
		++it;
	}
	cout << endl;
}

int main()
{
	//Test_vector1();
	//Test_vector2();
	/*Test_vector3();*/
	Test_vector4();

	return 0;
}