Replace values in array with surrounding null,0 - php

Question

So I have a collection of integer values, which is built from a result of another function that can have different values every time. Consider the following in PHP:
$arr = [0,0,2,2,0,0,0,3,3];
Which i need to convert to:
$newArr = [null,0,2,2,0,null,0,3,3];
What i want to accomplish is: If a value is > 0, its neighbours should be 0, and the rest should be null.
What is the best strategy here?

Answer 1

Playing with operator precedence:
$zero = true;
$arr = [0,0,2,2,0,0,0,3,3];
$newArr = [];
foreach($arr as $k=>$v) {
if ($v) {
$newArr[] = $v;
$zero = false;
} else {
if ($zero and isset($arr[$k+1]) && !$arr[$k+1] || !isset($arr[$k+1]))
$newArr[] = null;
else
$newArr[] = 0;
$zero = true;
}
}
print_r($newArr);

Answer 2

Looping through the entire array, we evaluate each element for three conditions:
1.Element is zero.
2.Previous element is set, and it is equal to zero or null.
3.Next element is set, and it is equal to zero or null.
<?php
foreach($array as $key => $element)
{
if($element == 0 && ((isset($array[$key - 1]) && !$array[$key - 1]) || (isset($array[$key + 1]) && !$array[$key + 1])))
{
$array[$key] = null;
}
}
?>

Answer 3

I think it should work for you:
<?php
$arr = [0,0,2,2,0,0,0,3,3];
$new_array = $arr;
$array_count = count($arr);
for ($i=0; $i<$array_count; $i++) {
if ($i == 0 && $arr[$i+1] == 0) {
$new_array[$i] = null;
} elseif ($i == ($array_count-1) && $arr[$i-1] == 0) {
$new_array[$i] = null;
} elseif ($arr[$i-1] == 0 && $arr[$i+1] == 0) {
$new_array[$i] = null;
}
}
echo "<pre>";
print_r($new_array);
?>

Answer 4

We need to check for three conditions: is there, prev. is zero and next is zero.
You can combine first two conditions into the third one.
Broke it down for simplicity.
$array = [0,0,2,2,0,0,0,3,3];
$newArray = [];
foreach ($array as $key => $val) {
$previous = NULL;
$next = NULL;
if (isset($array[$key + 1])) {
$next = $array[$key + 1];
}
if ($key != 0) {
$previous = $array[$key - 1];
}
if ($val === 0 && $next == 0 && $previous == 0) {
$newArray[] = 'NULL';
} else {
$newArray[] = $val;
}
}

Answer 5

Another way to do this:
$arr = [0,0,2,2,0,0,0,3,3];
foreach($arr as $key => $value){
if($arr[$key] > 0 && isset($arr[$key - 1]) && $arr[$key - 1] == 0){
if(isset($arr[$key - 2]) && $arr[$key - 2] == 0){
$arr[$key - 2] = null;
}
}
if($arr[$key] > 0 && isset($arr[$key + 1]) && $arr[$key + 1] == 0){
if(isset($arr[$key + 2]) && $arr[$key + 2] == 0){
$arr[$key + 2] = null;
}
}
}
echo '<pre>';
print_r($arr);
echo '</pre>';
Here, i am looking for the positive value first then checking and if neighbor is 0 then set neighbor's neighbor to null.

Answer 6

<?php
$arr = [0,0,2,2,0,0,0,3,3];
$extra = [];
for($x=0; $x<count($arr); $x++){
if($arr[$x] == 0){
$tmp = isset($tmp)?$tmp:[];
$tmp[]=$x;
}else{
if(isset($tmp)){
$extra[] = $tmp;
unset($tmp);
}
}
}
foreach($extra as $subArr){
if(count($subArr) == 2){
$arr[$subArr[0]] = null;
$arr[$subArr[1]] = 0;
}else if(count($subArr) == 3){
$arr[$subArr[0]] = 0;
$arr[$subArr[1]] = null;
$arr[$subArr[2]] = 0;
}
}
var_dump($arr);
// YIELDS::
array (size=9)
0 => null
1 => int 0
2 => int 2
3 => int 2
4 => int 0
5 => null
6 => int 0
7 => int 3
8 => int 3