C++ <list> pop_back function
pop_backis used in list todelete the element at the end of the linked listof the function.
pop_backis a member function of the container class, used to delete the last element of the linked list.
In the list,pop_backhas a time complexity of O(1), very efficient.
Word Definitions： popis to pop,backmeans "back/behind", and together it means popping the back element.
Basic syntax and parameters
pop_backis a member function of the container class, and calling it requires no parameters.
Syntax format
void pop_back();
Parameter description
- Parameter: No parameters
Function description
- Return Value：
void(No return value). - Effect: of the container
size()will decrease by 1. The last element is deleted. - Note: if the linked list is empty, call
pop_backIs undefined behavior.
Example
Example 1: Basic usage - deleting the last element
Example
#include <iostream>
#include <list>
int main() {
std::list<int> numbers = {10, 20, 30, 40, 50};
std::cout << "original list: ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
// Remove the last element
numbers.pop_back();
std::cout << "After pop_back(): ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
numbers.pop_back();
std::cout << "After pop_back() again: ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
return 0;
}
#include <list>
int main() {
std::list<int> numbers = {10, 20, 30, 40, 50};
std::cout << "original list: ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
// Remove the last element
numbers.pop_back();
std::cout << "After pop_back(): ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
numbers.pop_back();
std::cout << "After pop_back() again: ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
return 0;
}
Expected output:
原始 list: 10 20 30 40 50 pop_back() 后: 10 20 30 40 再 pop_back() 后: 10 20 30
Example 2: Safe Use of pop_back
Check whether the linked list is empty before use.
Example
#include <iostream>
#include <list>
void safePopBack(std::list<int>& lst) {
if(!lst.empty()) {
lst.pop_back();
std::cout << "Delete successful" << std::endl;
} else {
std::cout << "The list is empty, cannot delete" << std::endl;
}
}
int main() {
std::list<int> data = {1, 2, 3};
safePopBack(data);
safePopBack(data);
safePopBack(data);
safePopBack(data); // It is empty now
return 0;
}
#include <list>
void safePopBack(std::list<int>& lst) {
if(!lst.empty()) {
lst.pop_back();
std::cout << "Delete successful" << std::endl;
} else {
std::cout << "The list is empty, cannot delete" << std::endl;
}
}
int main() {
std::list<int> data = {1, 2, 3};
safePopBack(data);
safePopBack(data);
safePopBack(data);
safePopBack(data); // It is empty now
return 0;
}
Expected output:
Deletion successful Deletion successful Deletion successful The linked list is empty, cannot delete
other extensions