Delete enemy from vector array - c++

Question

This is my first question on this site. I learn programming for a year and I always found a answer for my problem in projects. I know that this is REALLY simple problem and here is a code:
#include "stdafx.h"
#include "Wave.h"
Wave::~Wave()
{
}
void Wave::setEnemyCount(int count) {
nemyCount = count;
}
bool Wave::createWave() {
for (int i = 0; i < enemyCount; i++) {
enemyArray.push_back(Enemy());
}
for (int i = 0; i < enemyArray.size(); i++) {
int randomPositionX = rand() % 150 + 10;
int randomPositionY = rand() % 50 + 10;
if (!enemyArray.at(i).init(randomPositionX, randomPositionY)) {
std::cout << "Create wave(init enemies) - failed\n";
return false;
}
}
return true;
}
void Wave::drawWave(Window* window) {
window->setCursor({ 0, 2 });
window->setColor(Window::Color::RED);
std::cout << "Enemies: " << enemyArray.size();
window->setColor(Window::Color::WHITE);
for (int i = 0; i < enemyArray.size(); i++) {
enemyArray.at(i).draw(window);
//std::cout << i;
}
}
void Wave::update(Bullet* bullet, Player* player) {
for (int i = 0; i < enemyArray.size(); i++) {
if (player->checkShoot()) {
if ((bullet->getPositionX() >= enemyArray.at(i).getPositionX() && bullet->getPositionX() <= enemyArray.at(i).getPositionX() + 5)) {
if ((bullet->getPositionY() >= enemyArray.at(i).getPositionY() && bullet->getPositionY() <= enemyArray.at(i).getPositionY() + 5)) {
player->addScore(10);
enemyArray.erase(enemyArray.begin() + i);
}
}
}
}
if (enemyArray.size() <= 0) {
std::cout << "WAVE COMPLETE";
Sleep(2000);
enemyCount += 5;
createWave();
}
}
int Wave::getEnemyCount() const {
return enemyCount;
}
The collision work correct, but when bullet touch a enemy of index for example: 5, a code always remove the enemy of last index, so I can remove each enemy only shoot to one enemy with index 5 or 1 or 7.

Answer 1

When you do enemyArray.erase(...) you shouldn't increment i because you will skip one element.
So you should rewrite the loop like this:
for (int i = 0; i < enemyArray.size();) {
if (player->checkShoot()) {
if ((bullet->getPositionX() >= enemyArray.at(i).getPositionX() && bullet->getPositionX() <= enemyArray.at(i).getPositionX() + 5)) {
if ((bullet->getPositionY() >= enemyArray.at(i).getPositionY() && bullet->getPositionY() <= enemyArray.at(i).getPositionY() + 5)) {
player->addScore(10);
enemyArray.erase(enemyArray.begin() + i);
continue;
}
}
}
++i;
}
Or, with a more idiomatic style:
for (auto it = enemyArray.begin(), end = enemyArray.end();it!=end;) {
if (player->checkShoot()) {
if ((bullet->getPositionX() >= it->getPositionX() && bullet->getPositionX() <= it->getPositionX() + 5)) {
if ((bullet->getPositionY() >= it->.getPositionY() && bullet->getPositionY() <= it->getPositionY() + 5)) {
player->addScore(10);
enemyArray.erase(it);
continue;
}
}
}
++it;
}
Of course, if you wan a single enemy to be removed at a time, you should break instead of continue in the loop, after having erased the element.
For completeness, you can also use std::remove_if if you want to remove all enemies touched by the bullet, it's more optimal than the 2 loops above, because it does less moving of elements when multiple elements are removed.