How do I delete an element from a vector?

Question

0.00/5 (No votes)

See more:

While I'm aware that this is just a simple thing to do, I've tried to make this into a function. While mine kind of works, I'm more interested in how other people would go about it.

C++

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

bool restart = true;
std::string choice;

bool inInventory(std::vector<std::string> vec, std::string inItem) {
    std::vector<std::string>::iterator invent;
    invent = std::find(vec.begin(), vec.end(), inItem);
    if (invent != vec.end()) {
        return true;
    } else {
        return false;
    }    
}

void dropItem(std::vector<std::string> vec, std::string itemToDrop) {
    std::vector<std::string>::iterator invent;
    invent = std::find(vec.begin(), vec.end(), itemToDrop);
    if (inInventory(vec, itemToDrop)) {
        std::remove(vec.begin(), vec.end(), itemToDrop);
    } else {
        std::cout << "Item is not in vector!\n";
        restart = true;
    }
}

int main() {
    
    std::vector<std::string> shoppingList;

    shoppingList.push_back("Butter");
    shoppingList.push_back("Cheese");
    shoppingList.push_back("Candy");
    while (restart) {
        restart = false;
        for (auto e: shoppingList) {
            std::cout << e << ", ";
        }
    
        std::cout << "Pick an item to drop\n>";
        std::cin >> choice;
        dropItem(shoppingList, choice);
    
        for (auto e: shoppingList) {
            std::cout << e << ", ";
        }
        return 0;
    }
}

Here is the code in case anyone is interested.

BTW: I'm not requesting anyone to fix this. I'm just wondering how the process would go for those more skilled than me.

Thanks!

What I have tried:

Messing around with functions and vectors, mainly the std::remove(); function.

Posted 11-Sep-23 14:26pm

Brennon Nevels

Updated 12-Sep-23 11:32am

Deeksha Shenoy

v3

Add a Solution

3 solutions

Solution 2

With C++ 20, the single line

C++

std::erase(shoppingList, choice);

would do the trick. See std::erase, std::erase_if (std::vector) - cppreference.com[^].

Posted 11-Sep-23 21:36pm

CPallini

Comments

Brennon Nevels 12-Sep-23 5:33am

5

CPallini 12-Sep-23 5:41am

Thank you.

Solution 3

If the order of elements in the vector isn't important, an efficient way to do this is to move the last element into the slot of the element being erased. This is how I manage the list of open sockets for the poll function, and I wrote a simple article describing a class template that does this while otherwise reusing std::vector:

A Wrapper for std::vector[^]

Posted 12-Sep-23 4:41am

Greg Utas

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Rick York · Accepted Answer · 2023-09-11T14:37:00

That is done use the erase method of the vector class : https://cplusplus.com/reference/vector/vector/erase/[^]. It can be a very expensive operation to perform if deleting from anywhere except the tail end of the vector. If deletions are going to be common then you should consider using a std::list or std::deque. Both of those accommodate additions and deletions very well. The downside is you can't access elements quite as easily as you can with a vector. They support iterators like vector does though so that style of access is consistent. For vectors of simple types deletion is not terribly expensive although it requires reallocation and copying of data. That is why it is expensive for types that are more complex.

Here is documentation on those classes :
https://cplusplus.com/reference/list/list/[^]
https://cplusplus.com/reference/deque/deque/[^]