How to Erase Element from Vector in C++: Syntax and Examples

To erase an element from a std::vector in C++, use the erase() method with an iterator pointing to the element you want to remove. You can erase a single element or a range of elements by passing iterators to erase().

Syntax

The erase() method removes elements from a std::vector. It takes either a single iterator or a range of iterators.

• vec.erase(pos); removes the element at the position pos.
• vec.erase(first, last); removes all elements in the range from first up to but not including last.

After erasing, the vector shifts elements to fill the gap and reduces its size.

cpp

vec.erase(iterator position);
vec.erase(iterator first, iterator last);

Example

This example shows how to erase a single element and a range of elements from a vector.

cpp

#include <iostream>
#include <vector>

int main() {
    std::vector<int> vec = {10, 20, 30, 40, 50};

    // Erase the element at index 2 (value 30)
    vec.erase(vec.begin() + 2);

    // Erase elements from index 1 to 3 (values 20 and 40)
    vec.erase(vec.begin() + 1, vec.begin() + 3);

    // Print remaining elements
    for (int val : vec) {
        std::cout << val << " ";
    }
    return 0;
}

Output

10 50 

Common Pitfalls

Common mistakes when erasing elements from a vector include:

• Using an invalid iterator after erasing, since erase() invalidates iterators at and after the erased position.
• Trying to erase elements by value directly (like vec.erase(30);) which is incorrect; you must use iterators.
• Not updating iterators when erasing elements inside a loop, which can cause skipping elements or crashes.

cpp

#include <vector>
#include <iostream>
#include <algorithm>

int main() {
    std::vector<int> vec = {1, 2, 3, 4, 5};

    // Wrong: trying to erase by value (won't compile)
    // vec.erase(3); 

    // Correct: find iterator to element with value 3 and erase
    auto it = std::find(vec.begin(), vec.end(), 3);
    if (it != vec.end()) {
        vec.erase(it);
    }

    // Erasing inside a loop - wrong way (skips elements)
    // for (auto it = vec.begin(); it != vec.end(); ++it) {
    //     if (*it % 2 == 0) {
    //         vec.erase(it); // iterator invalidated
    //     }
    // }

    // Correct way: use iterator returned by erase
    for (auto it = vec.begin(); it != vec.end(); ) {
        if (*it % 2 == 0) {
            it = vec.erase(it); // erase returns next valid iterator
        } else {
            ++it;
        }
    }

    for (int v : vec) std::cout << v << " ";
    return 0;
}

Output

1 3 5 

Quick Reference

Remember these tips when erasing elements from a vector:

• Use erase() with iterators, not values.
• Erasing invalidates iterators at and after the erased position.
• When erasing in loops, update the iterator with the return value of erase().
• To remove elements by value, combine std::remove and erase() (the erase-remove idiom).

Key Takeaways

Use vector's erase() method with iterators to remove elements safely.

Erase invalidates iterators at and after the erased position; update iterators accordingly.

To erase elements by value, find their iterator first or use the erase-remove idiom.

When erasing inside loops, assign the iterator to the erase() return value to avoid skipping elements.