C++ .pop_back()

In C++, the .pop_back() method removes the element at the back of a deque.

If the deque is empty, calling .pop_back() results in undefined behavior (UB), meaning the program might crash or behave unpredictably. To prevent this, always check if the deque is not empty using .empty() before calling .pop_back().

Syntax

dequeName.pop_back();

Parameters:

.pop_back() method does not take any parameters.

Return value:

The .pop_back() method does not return a value.

Example

The example below showcases the use of the .pop_back() method, with a safety check using .empty() to avoid UB:

#include <iostream>
#include <deque>

int main() {

  // Initialize a deque of integers with 4 elements
  std::deque<int> numbers = {10, 20, 30, 40};

  // Check if the deque contains elements
  if (!numbers.empty()) {

    // Display the last element from the deque before removal
    std::cout << "Last element: " << numbers.back() << std::endl;

    // Remove the last element from the deque
    numbers.pop_back();

    // Display the new last element from the deque after removal
    std::cout << "New last element: " << numbers.back() << std::endl;
  } else {

    // Display if the deque is empty
    std::cout << "Deque is empty" << std::endl;
  }

  return 0;
}

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The above code generates the following output:

Last element: 40
New last element: 30

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Codebyte Example

The following codebyte removes the last element from myDeque using the .pop_back() method and displays the updated size of the deque:

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