Basic usage of STL list

The bottom layer of list is actually a doubly linked list structure.

Use of list

Constructor and assignment overloading

Constructor	illustrate
list()	No-argument construction
list (size_type n, const value_type& val = value_type())	The constructed list contains n elements whose value is val
list (const list& x)	copy constructor
list (InputIterator first, InputIterator last)	Constructs a list with elements in the range [first, last)

The constructor is used the same as the previous container

void test1()
{
    
    
	list<int> lt1;//无参构造

	list<int> lt2(10, 1);//1,1,1,1,1,1,1,1,1,1

	list<int> lt3(lt2);//拷贝构造

	list<int> lt4(lt2.begin(), lt2.end());
}

Assignment overloading

list& operator= (const list& x);

void test1()
{
    
    
	list<int> lt1;//无参构造

	list<int> lt2(10, 1);//1,1,1,1,1,1,1,1,1,1

	list<int> lt3(lt2);//拷贝构造

	list<int> lt4(lt2.begin(), lt2.end());

	list<int> lt5;
	lt5 = lt4;//赋值重载
}

---

Iterator (most important)

There are three types of iterators: one-way iterators, two-way iterators, and random iterators

One-way iterator: supports ++ For example, the iterator type of forward_list and hash is a one-way iterator
Bidirectional iterator: supports ++, - - For example, the iterator type of list, map, set is a two-way iterator
Random iterator: Supports ++, - -, +, -. For example, the iterator types of vector, string, and deque are random iterators.

Random iterators can be thought of as special bidirectional iterators, and bidirectional iterators can be thought of as special unidirectional iterators

The iterator of list is different from vectorand The type of iterator is determined by the underlying structure of the containerstring

vectorThe bottom layer of and stringis continuous, so their iterators are actually pointers, so they support ++, –, +, -, and the type is a random iterator

However list, the bottom layer of the . to iterator

For unsupported +, -this packaging is because: it.begin()+5the efficiency like this is too low, C++ does not support

The iterator of the list does not support the one in the vector it.begin()+5, if written like this, an error will be reported

Only supports ++,--

void test2()
{
    
    
	list<int> lt{
    
     1,2,3,4,5,6 };
	lt.begin()--;
	lt.begin()++;
}

If you want to move listthe iterator to multiple positions like vectorin , you can only do this:it.begin()+5

void test2()
{
    
    
	list<int> lt{
    
     1,2,3,4,5,6 };
	list<int>::iterator it = lt.begin();
	for (size_t i = 0; i < 5; i++)
	{
    
    
		++it;
	}
}

For the rest, listthe iterator also supports the previous functions, and the usage is the same

---

Capacity related

empty

bool empty() const;

Determine whether the container is empty

size

size_type size() const;

Returns the number of elements in the container

---

insert delete

listAs a two-way circular linked list, the efficiency of head insertion, head deletion, tail insertion, and tail deletion is very high, so these operations are supported in the list

function	illustrate
void push_front (const value_type& val);	Insert an element with value val before the first element of the list
void pop_front();	delete the first element in the list
void push_back (const value_type& val);	Insert an element with value val at the end of the list
void pop_back();	delete the last element in the list

void test3()
{
    
    
	list<int> lt{
    
     1,2,3,4,5,6 };
	lt.push_back(10);
	lt.push_front(0);
	lt.pop_back();
	lt.pop_front();
}

insert

iterator insert (iterator position, const value_type& val);

void insert (iterator position, size_type n, const value_type& val);
	
template <class InputIterator>
    void insert (iterator position, InputIterator first, InputIterator last);

insertThe operation vectoris the same as that used in , but this insertwill not cause the iterator to fail
because the insertion of the linked list must be expanded. If the iterator points to a certain node, the iterator still points to the original node after insertion, which will not lead to failure

erase

iterator erase (iterator position);
iterator erase (iterator first, iterator last);

erase The operation vectoris the same as that in , which erase will cause the iterator to be invalid.
The iterator points to a certain node. After deleting this node, the iterator becomes invalid.

---

Element operations

reverse

void reverse();

This reverseis lista function that comes with the class, and its function is to reverse the linked list

There <algorithm>is also a reversefunction
reversein which the iterator type is a bidirectional iterator, and the iterator type of list is a bidirectional iterator, so list can also be used <algorithm>inreverse

void test4()
{
    
    
	list<int> lt{
    
     1,2,3,4,5,6 };
	lt.reverse();
	reverse(lt.begin(), lt.end());
}

---

sort

void sort();

<algorithm>The function is sorting, and there are also functions in the bottom layer of merging sort, but for lists, if you want to sort, you can only use the functions listin the library , and there are sortfunctions that cannot be used<algorithm>sort

Because the iterator type of list is a bidirectional iterator, and the parameter iterator type of is a random iterator, so the function of list cannot <algorithm>be used .sort<algorithm>sort

In fact, the meaning here sortis not great, because compared to the low efficiency <algorithm>of the medium ( the bottom layer of the medium uses merging, and the medium uses quick sorting), and the only meaning is: convenient, the amount of data is small, you can shoot, but the amount of data is larger If it's too big, don't use it .sortlistsort<algorithm>sort
listsort

If you want to sort, you can listcopy the data in the middle to vectorthe middle, and then sort , and then copy the data to the middle vectorafter sortinglist

void test5()
{
    
    
	list<int> lt{
    
     5,7,3,9,1,0,4,7,8,9,4, };
	vector<int> v;

	//将数据从list拷贝到vector
	for (auto e : lt)
	{
    
    
		v.push_back(e);
	}

	//在vector中排序
	reverse(v.begin(), v.end());

	//再把数据从vector拷贝到list中
	for (auto e : v)
	{
    
    
		lt.push_back(e);
	}
}

---

unique

void unique();

The function is to remove duplicates, but it needs to be sorted first.

void test6()
{
    
    
	list<int> lt{
    
    2,6,5,2,2,2,2};
	lt.sort();
	lt.unique();// 5,6
}

---

remove

void remove (const value_type& val);

The function of remove is to find all the positions first val, and then erasedrop all theval

void test6()
{
    
    
	list<int> lt{
    
    1,2,3,4,5,6,6,7,8};

	//移除元素6
	lt.remove(6);//1,2,3,4,5,7,8
}

---

splice

void splice (iterator position, list& x);

void splice (iterator position, list& x, iterator i);
	
void splice (iterator position, list& x, iterator first, iterator last);

The function of splice is to transfer nodes

• void splice (iterator position, list& x), xtransfer all elements in the linked list to positionposition
• void splice (iterator position, list& x, iterator i), transfer the element at position xin the linked list to positioniposition
• void splice (iterator position, list& x, iterator first, iterator last), xtransfer the elements in [first,last) in the linked list to positionthe position

void test7()
{
    
    
	list<int> lt1{
    
     1,2,3,4,5,6,7 };
	list<int> lt2{
    
     0,0 };

	lt2.splice(++lt2.begin(), lt1);

	for (auto e : lt1)
	{
    
    
		cout << e << " ";
	}//lt1中的元素转移空了
	cout << endl;

	for (auto e : lt2)
	{
    
    
		cout << e << " ";
	}//0 1 2 3 4 5 6 7 0
	cout << endl;


	list<int> lt3{
    
     1,2,3,4,5,6,7 };
	list<int> lt4{
    
     0,0 };

	lt4.splice(++lt4.begin(), lt3, ++lt3.begin());
	for (auto e : lt3)
	{
    
    
		cout << e << " ";
	}//1 3 4 5 6 7
	cout << endl;

	for (auto e : lt4)
	{
    
    
		cout << e << " ";
	}//0 2 0
	cout << endl;


	list<int> lt5{
    
     1,2,3,4,5,6,7 };
	list<int> lt6{
    
     0,0 };

	lt6.splice(++lt6.begin(), lt5,++++lt5.begin(), --lt5.end());
	for (auto e : lt5)
	{
    
    
		cout << e << " ";
	}//1 2 7
	cout << endl;

	for (auto e : lt6)
	{
    
    
		cout << e << " ";
	}//0 3 4 5 6 0
	cout << endl;
}