The array of articles to learn c ++

Array

C ++ 11's traversal cycle optimization

format:

for (variable type variable name: array name)

• Here variable types can also be used to fill a member type auto type
• If the conversion is inconsistent and may be, for default forwarding strong

example:

int Students[5]{}; //学号
int num = sizeof(Students) / sizeof(int);
for (int i = 0; i < num; ++i)
{
	cout << "请输入第" << i + 1 << "个学生的学号:";
	cin >> Students[i];
}
//for (int i : Students)   //可以用这个
for (auto i : Students) //也可以用这个
{
	cout << i << endl;
}

Review multidimensional arrays

Two-dimensional array traversal:

	int students[3][3]
	{ 
		{1,2,3},
		{4,5,6},
		{7,8,9}
	};
	for (int i = 0; i < 3; i++)
	{
		for (auto j : students[i]) //用上c++11的新方法，挺好的
		{	
			cout << j << " ";
		}
		cout << endl;
	}

Three-dimensional array is similar, the code is given here:

	int students[2][2][2]
	{ 
		{
			{1,2},
			{3,4},
		},
		{
			{5,6},
			{7,8},
		}
	};
	for (int i = 0; i < 2; i++)
	{
		for (int j = 0; j < 2; j++)
		{
			for (auto k : students[i][j])
			{
				cout << k << " ";
			}
			cout << endl;
		}
		cout << endl;
	}

Results:

Array Caution:

• Unless forced to use an array, otherwise not all; because this is a cross-border loopholes commonplace problem, the program is likely to produce unpredictable errors or being attacked!

• Multi-dimensional arrays in accordance with the operating system memory of most low-dimensional prioritization

array of review

Common Operations

• size () is used to query the size of the container
• fill (const int) for initializing all
• at (num) for secure access to (cross-border will throw an exception)
• Overloaded [], similar to the array access, it will be out of bounds
• It can be used to compare two reload ==

These are the most basic usage!

Sample code:

	std::array<int, 3> StusID{};
	std::array<int, 3> _StusID{25,25,25};
	cout << "size = " << StusID.size() << endl;
	StusID.fill(25);
	for (int i = 0; i < StusID.size(); i++)
	{
		//cout << "stu[" << i << "] = " << StusID[i] << endl;  //不安全
		cout << "stu[" << i << "] = " << StusID.at(i) << endl;
	}
	if (StusID == _StusID)cout << "相等" << endl;
	else  cout << "不相等" << endl;

result:

vector of the review

Common Operations

1, the initialization operation

There are five ways, seen below:

std::vector<int> StuID1; //空容器
std::vector<int> StuID2{ 3,4,5 }; //有三个数
std::vector<int> StuID3(5); //有五个数，并全为0
std::vector<int> StuID4(3,50); //3个数，全为50

The results show visit:

2, a common method

• push_back (value) is inserted into the container a number
• assign (num, value) the container is re-initialized values ​​of num value
• clear () empty vessel
• empty () return a container is empty, otherwise 0
• at (num) secure access to the container contents (cross-border Throws)

Sample code:

	std::vector<int> StuID1; //定义空容器
	StuID1.push_back(5); //插入一个5
	StuID1.push_back(10); //插入一个10
	for (int i = 0; i < StuID1.size(); i++) //遍历
	{
		cout << "Stu1 [" << i << "] = " << StuID1.at(i) << " ";
	}
	cout << endl;
	StuID1.assign(3, 8);  //重新初始化
	for (int i = 0; i < StuID1.size(); i++)
	{
		cout << "Stu1 [" << i << "] = " << StuID1.at(i) << " ";
	}
	cout << endl;
	StuID1.clear(); //清空
	if (StuID1.empty())cout << "空的" << endl;
	else cout << "不是空的" << endl;

Results:

thanks to their own hard work! ! !