如何在php中循环迭代数组循环？

Question

Suppose i have a number let's say 5. Now lets assume that there are 5 members. Now each member started to count 1 to 2. Those member who get 2nd number leaves and then again count start from the next member. so at last in this scenario the 3rd member stays at last.

So i tried to implement like this. First of assign members as array $v.

for($i=1 ; $i<=5 ; $i++)
{
    $v[] = $i;
}

$v1 = array_flip($v);

for($i=0 ; $i<=5 ; $i += 2 )
{   
    unset($v1[$i]);
}

echo "<pre>";
print_r($v1);

output

Array
(
    [1] => 0
    [3] => 2
    [5] => 4
)

Now i want to count the numbers from key 5(5th member) to again 1(1st member) and so on.

so at last key 3(3rd member) left.
I want to print the last member that left.

How can i achieve this?

I you can't understand then look at this Survival Strategy

Answer 1

Here's an Object-Oriented solution with an easy-to-follow reduce method and multiple examples.

class CountByTwoArrayReducer {

  public function __construct($array) {
    $this->array = $array;
    $this->size  = count($array);
  }

  public function reduce() {
    $this->initialize();

    while($this->hasMultipleItems()) {
      $this->next();
      $this->removeCurrentItem();
      $this->next();
    }

    return $this->finalItem();
  }

  protected function initialize() {
    $this->current   = 1;
    $this->removed   = array();
    $this->remaining = $this->size;
  }

  protected function hasMultipleItems() {
    return ($this->remaining > 1);
  }

  protected function next($start = null) {
    $next = ($start === null) ? $this->current : $start;

    do {
      $next++;
    } while(isset($this->removed[$next]));

    if($next > $this->size)
      $this->next(0);
    else
      $this->current = $next;
  }

  protected function removeCurrentItem() {
    $this->removed[$this->current] = 1;
    $this->remaining--;
  }

  protected function finalItem() {
    return $this->array[$this->current - 1];
  }

}

$examples = array(
  array('A', 'B', 'C', 'D', 'E'),
  range(1, 100),
  range(1, 1000),
  range(1, 10000)
);

foreach($examples as $example) {
  $start = microtime(true);

  $reducer = new CountByTwoArrayReducer($example);
  $result  = $reducer->reduce();

  $time = microtime(true) - $start;

  echo "Found {$result} in {$time} seconds.
";
}