C++ <list> push_back function

C++ container class <list>

Among the many containers,list(Doubly linked list) is a data structure with efficient insertion and deletion, andpush_backis the key function for adding elements at the end of the linked list.

push_backis a member function used tolinked list (list)ofendAdd a new element.

push_backimplements a linked listdynamic growth, you don't need to pre-specify the final size of the container, and can add elements anytime and anywhere as needed during program runtime.

Word Definitions： pushis pushing,backmeans "the back", so together it means "push to the back", which is very vivid.

Basic syntax and parameters

push_backis a member function of container classes, so you need to have a container object first, and then use the dot operator.to call it.

Syntax format

void push_back(const T& value);
void push_back(T&& value);  // C++11 之后（支持右值）

Parameter description

  • Parameter： value
    • Type: consistent with the element type specified when the container was defined, or a value that can be converted to that type.
    • Description: the value you want to add to the end of the container. It can be a variable, a literal (such as10, "hello"), or the result of an expression.

Function description

  • Return Value： void(no return value). Its purpose is purely "adding an element"; once the addition is complete, the function ends.
  • Effect: of the containersize()(current number of elements) will increase by 1. The new element becomes the last element of the linked list.

Example

Let's thoroughly master it through a series of examples, from simple to complex:push_backUsage.

Example 1: Basic usage - managing integers

Example

#include <iostream>
#include <list> // 1. Must include the list header file

int main() {
    // 2. Create an empty list to store integers
    std::list<int> numbers;

    std::cout << "Initially, the size of the list is: " << numbers.size() << std::endl;

    // 3. Use push_back to add elements
    numbers.push_back(10); // Add integer 10 at the end
    numbers.push_back(20); // Add 20 after 10
    numbers.push_back(30); // Add 30 after 20

    std::cout << "After adding, the size of the list is: " << numbers.size() << std::endl;

    // 4. Traverse and output all elements
    std::cout << "The elements in the list are: ";
    for(int n : numbers) {
        std::cout << n << " ";
    }
    std::cout << std::endl;

    return 0;
}

Expected output:

初始时，list的大小是: 0
添加后，list的大小是: 3
list中的元素是: 10 20 30

Code analysis:

  1. #include <list>is to uselistThe premise of a container.
  2. std::list<int> numbers;Created one namednumbersof the emptylist, which will later storeintintegers of type.
  3. three timespush_backcall, sequentially10, 20, 30add tonumbersend. The order of addition is the elements inlistthe final order in
  4. numbers.size()Returns the current number of elements.

Example 2: Managing strings

listIt can store not only numbers, but also strings, custom types, and any other data type.

Example

#include <iostream>
#include <list>
#include <string>

int main() {
    // Create a list that stores std::string
    std::list<std::string> tasks;

    // Use push_back to add to-do items
    tasks.push_back("Learn C++ list");
    tasks.push_back("Do homework");
    tasks.push_back("Read technical documentation");

    std::cout << "Today's to-do items (" << tasks.size() << " items):" << std::endl;
    for(const auto& task : tasks) {
        std::cout << "- " << task << std::endl;
    }

    return 0;
}

Expected output:

今日待办事项 (3 项):
- 学习 C++ list
- 写作业
- 阅读技术文档

Code analysis:

  • std::list<std::string>declares the element type asstd::stringcontainer.
  • push_backThe parameter is a string literal.

Example 3: Using with push_front

push_backandpush_frontcan be used together to build a linked list.

Example

#include <iostream>
#include <list>

int main() {
    std::list<int> data;

    // First add at the head
    data.push_front(30);
    data.push_front(20);
    data.push_front(10);

    // Then add at the tail
    data.push_back(40);
    data.push_back(50);

    std::cout << "Elements: ";
    for(int n : data) {
        std::cout << n << " ";
    }
    std::cout << std::endl;

    return 0;
}

Expected output:

元素: 10 20 30 40 50

Code analysis:

  • First usepush_frontAdd 10, 20, 30 at the head
  • Then usepush_backAdd 40, 50 at the tail
  • The final order is 10 -> 20 -> 30 -> 40 -> 50

C++ container class <list>

other extensions