C++ <list> pop_front function
pop_frontis used in the list toremove the head element of the linked listThe function is one of the characteristic operations of a linked list.
pop_frontIt is a member function of the container class, used to delete the first element of a linked list.
Unlike vector,listThe time complexity of deleting an element at the head is O(1), which is very efficient.
Word Definitions： popis to pop,frontmeans "front"; together, it means popping the front element.
Basic syntax and parameters
pop_frontIt is a member function of the container class; calling it requires no parameters.
Syntax format
void pop_front();
Parameter description
- Parameter: No parameters
Function description
- Return Value：
void(No return value). - Effect: of the container
size()will decrease by 1. The first element is deleted. - Note: if the linked list is empty, call
pop_frontis undefined behavior.
Example
Example 1: Basic usage - deleting the head 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;
// Delete the head element
numbers.pop_front();
std::cout << "after pop_front(): ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
numbers.pop_front();
std::cout << "after pop_front() 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;
// Delete the head element
numbers.pop_front();
std::cout << "after pop_front(): ";
for(int n : numbers) std::cout << n << " ";
std::cout << std::endl;
numbers.pop_front();
std::cout << "after pop_front() 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_front() 后: 20 30 40 50 再 pop_front() 后: 30 40 50
Example 2: Implementing a queue
Usagepush_backandpop_frontCan implement a queue.
Example
#include <iostream>
#include <list>
#include <string>
class Queue {
private:
std::list<std::string> data;
public:
void enqueue(const std::string& item) {
data.push_back(item);
}
void dequeue() {
if(!data.empty()) {
data.pop_front();
}
}
std::string front() const {
return data.front();
}
bool empty() const {
return data.empty();
}
size_t size() const {
return data.size();
}
};
int main() {
Queue q;
q.enqueue("User A");
q.enqueue("User B");
q.enqueue("User C");
std::cout << "Queue size: " << q.size() << std::endl;
while(!q.empty()) {
std::cout << "Processing: " << q.front() << std::endl;
q.dequeue();
}
return 0;
}
#include <list>
#include <string>
class Queue {
private:
std::list<std::string> data;
public:
void enqueue(const std::string& item) {
data.push_back(item);
}
void dequeue() {
if(!data.empty()) {
data.pop_front();
}
}
std::string front() const {
return data.front();
}
bool empty() const {
return data.empty();
}
size_t size() const {
return data.size();
}
};
int main() {
Queue q;
q.enqueue("User A");
q.enqueue("User B");
q.enqueue("User C");
std::cout << "Queue size: " << q.size() << std::endl;
while(!q.empty()) {
std::cout << "Processing: " << q.front() << std::endl;
q.dequeue();
}
return 0;
}
Expected output:
队列大小: 3 处理: 用户A 处理: 用户B 处理: 用户C
other extensions