We have discussed List and some of its functions in the following article:
Some more useful functions are discussed in this article
1. emplace(position, value) :- This function is used to insert an element at the position specified. 在特定位置插入值
2. emplace_back(value) :- This function adds value at end of list. It is different from push_back() by the fact that it directly creates element at position whereas push_back() first makes a temporary copy and copies from there. emplace_back() is faster in implementation than push_back() in most situations. 函数在list的最后插入值，和push_back不同，它直接在那个位置创建元素，而push_back首先创建临时的副本，然后复制到那里，大多情况下emplace_back比push_back快。
3. emplace_front :- This function adds value at beginning of list. It is different from push_front() by the fact that it directly creates element at position whereas push_front() first makes a temporary copy and copies from there. emplace_front() is faster in implementation than push_front() in most situations. 在list的前面插入值，和push_front不同，直接在那个位置创建值，而push_front是创建临时的副本，然后复制到那里，emplace_front比push_front快。
// C++ code to demonstrate the working of
// emplace(), emplace_front() and emplace_back()
#include<iostream>
#include<list> // for list functions
using namespace std;
int main()
{
// Declaring a list
list<int> gqlist;
// Initialising list iterator
list<int>::iterator it= gqlist.begin();
// Entering list element using emplace_back()
for (int i=1; i<=5; i++)
gqlist.emplace_back(i);
// Displaying list elements
cout << "List after emplace_back operation is : ";
for (int &x : gqlist) cout << x << " ";
cout << endl;
// Entering list element using emplace_front()
for (int i=10; i<=50; i+=10)
gqlist.emplace_front(i);
// Displaying list elements
cout << "List after emplace_front operation is : ";
for (int &x : gqlist) cout << x << " ";
cout << endl;
// using advance() to advance iterator position
advance(it,2);
// inserting element at 2nd position using emplace()
gqlist.emplace(it,100);
// Displaying list elements
cout << "List after emplace operation is : ";
for (int &x : gqlist) cout << x << " ";
cout << endl;
return 0;
}
Output:
List after emplace_back operation is : 1 2 3 4 5
List after emplace_front operation is : 50 40 30 20 10 1 2 3 4 5
List after emplace operation is : 50 100 40 30 20 10 1 2 3 4 5
4. merge(list2) :- This function is used to merge list2 with list1. If both the lists are in sorted order, then the resulting list is also sorted.把list1和list2融合到一起，如果两个list都是有序的，那么结果也是有序的。
5. remove_if(condition) :- This function removes the element from list on the basis of condition given in its argument. 如果条件符合，则删除符合条件的元素。
// C++ code to demonstrate the working of
// merge() and remove_if()
#include<iostream>
#include<list> // for list functions
using namespace std;
int main()
{
// Initializing list1
list<int> gqlist1 = {1, 2, 3};
// Initializing list2
list<int> gqlist2 = {2, 4, 6};
// using merge() to merge list1 with list2
gqlist1.merge(gqlist2);
// Displaying list elements
cout << "list1 after merge operation is : ";
for (int &x : gqlist1) cout << x << " ";
cout << endl;
// using remove_if() to remove odd elements
// removes 1 and 3
gqlist1.remove_if([](int x){return x%2!=0;});
// Displaying list elements
cout << "list1 after remove_if operation is : ";
for (int &x : gqlist1) cout << x << " ";
cout << endl;
return 0;
}
Output:
list1 after merge operation is : 1 2 2 3 4 6
list1 after remove_if operation is : 2 2 4 6
6. unique() :- This function is used to delete the repeated occurrences of the number. List has to be sorted for this function to get executed. 删除重复出现的元素，list必须是有序的。
7. splice(position, list2) :- This function is used to transfer elements from one list into another.把一个list中的元素传送到另一个list。
// C++ code to demonstrate the working of
// unique() and splice()
#include<iostream>
#include<list> // for list functions
using namespace std;
int main()
{
// Initializing list1
list<int> gqlist1 = {1, 1, 1, 2, 2, 3, 3, 4};
// Initializing list2
list<int> gqlist2 = {2, 4, 6};
// Initializing list1 iterator
list<int>::iterator it = gqlist1.begin();
// using advance() to increment iterator position
advance(it, 3);
// Displaying list elements
cout << "list1 before unique operation is : ";
for (int &x : gqlist1) cout << x << " ";
cout << endl;
// using unique() to remove repeating elements
gqlist1.unique();
// Displaying list elements
cout << "list1 after unique operation is : ";
for (int &x : gqlist1) cout << x << " ";
cout << endl << endl;
// using splice() to splice list2 in list1 at position it
// inserts list2 after 2nd position
gqlist1.splice(it, gqlist2);
// Displaying list elements
cout << "list1 after splice operation is : ";
for (int &x : gqlist1) cout << x << " ";
cout << endl;
return 0;
}
Output:
list1 before unique operation is : 1 1 1 2 2 3 3 4
list1 after unique operation is : 1 2 3 4
list1 after splice operation is : 1 2 4 6 2 3 4
8. swap(list2) :- This function is used to swap one list element with other. 交换两个list的元素。
// C++ code to demonstrate the working of
// swap()
#include<iostream>
#include<list> // for list functions
using namespace std;
int main()
{
// Initializing list1
list<int> gqlist1 = {1, 2, 3, 4};
// Initializing list1
list<int> gqlist2 = {2, 4, 6};
// Displaying list before swapping
cout << "The contents of 1st list "
"before swapping are : ";
for (int &x : gqlist1)
cout << x << " ";
cout << endl;
cout << "The contents of 2nd list "
"before swapping are : ";
for (int &x : gqlist2)
cout << x << " ";
cout << endl;
// Use of swap() to swap the list
gqlist1.swap(gqlist2);
// Displaying list after swapping
cout << "The contents of 1st list "
"after swapping are : ";
for (int &x : gqlist1)
cout << x << " ";
cout << endl;
cout << "The contents of 2nd list "
"after swapping are : ";
for (int &x : gqlist2)
cout << x << " ";
cout << endl;
return 0;
}
Output:
The contents of 1st list before swapping are : 1 2 3 4
The contents of 2nd list before swapping are : 2 4 6
The contents of 1st list after swapping are : 2 4 6
The contents of 2nd list after swapping are : 1 2 3 4
This article is contributed by Manjeet Singh .If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to [email protected]. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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