YouTipCpp Libs Vector Pop_Back
[ C++ Container Class ](#)
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Among many container operations, `pop_back` is a very practical function used to **delete the element at the end of the vector**.
`pop_back` is a member function of the container class, used to delete the last element of the container, and the container's `size()` will decrease by 1.
`pop_back` implements the **dynamic shrinking** of the container, allowing you to remove unneeded trailing elements at any time.
**Word Meaning**: `pop` means to pop out, `back` means the back/rear, together they mean popping the element at the back, which is very vivid.
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## Basic Syntax and Parameters
`pop_back` is a member function of the container class, so you need to have a container object first, and then call it via the dot operator `.`.
### Syntax Format
void pop_back();
### Parameter Description
* **Parameters**: No parameters
* `pop_back` does not accept any parameters.
### Function Description
* **Return Value**: `void` (no return value). Its role is purely to "delete the element", and the function ends after the deletion is complete.
* **Effect**: The `size()` of the container (current number of elements) will decrease by 1. The original last element is deleted.
* **Note**: If the container is empty, calling `pop_back` is undefined behavior. You should check if the container is empty before calling it (using the `empty()` function).
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## Examples
Let's thoroughly master the usage of `pop_back` through a series of examples from simple to complex.
### Example 1: Basic Usage - Deleting the Last Element
## Instance
#include
#include // 1. Must include the vector header file
int main(){
// 2. Create a vector and add some elements
std::vector numbers ={10, 20, 30, 40, 50};
std::cout<<"Initially, the size of the vector is: "<< numbers.size()<< std::endl;
std::cout<<"Elements are: ";
for(int n : numbers){
std::cout<< n <<" ";
}
std::cout<< std::endl;
// 3. Use pop_back to delete the last element
numbers.pop_back();// Delete the last element (50)
std::cout<<"After deleting one element, the size is: "<< numbers.size()<< std::endl;
numbers.pop_back();// Delete the last element (40)
std::cout<<"After deleting another element, the size is: "<< numbers.size()<< std::endl;
// 4. Traverse and output all elements
std::cout<<"Remaining elements are: ";
for(int n : numbers){
std::cout<< n <<" ";
}
std::cout<< std::endl;
return 0;
}
**Expected Output:**
Initially, the size of the vector is: 5Elements are: 10 20 30 40 50After deleting one element, the size is: 4After deleting another element, the size is: 3Remaining elements are: 10 20 30
**Code Analysis:**
1. `#include ` is a prerequisite for using the `vector` container.
2. `std::vector numbers = {10, 20, 30, 40, 50};` creates a `vector` containing 5 elements.
3. Two `pop_back` calls sequentially delete the trailing `50` and `40`.
4. After each call, the `size()` of the container decreases by 1.
### Example 2: Safe Use of pop_back - Checking if the Container is Empty
Before calling `pop_back`, it is best to check if t