Hey everyone I have a question about arrays and loops in PHP.
For a game I'm making, I need to write a function that generates a stack of crystal_id's based on a given size and ratio.
The ratio is the ratio between black crystals and different colored crystal (so a ratio of 0,25 (1:4) and a stack of 50 would yield a stack with 40 black crystals and 10 colored crystals).
I have all the math to calculate the amount of crystals per color and stuff figured out, but I can't figure out how to create an array with the right amount of colored crystals where each color is represented equally.
For reference, the array the code gets to choose from is a variable called $crystals_array, which is an array filled with integers where each integer represents a different colored crystal (e.g. [2,3,4,5,6]).
In the above case we have 5 different colored crystals and we needed a total of 10 colored crystals where each crystal is represented equally. So I need to create an array that looks a little something like this:
[2,2,3,3,4,4,5,5,6,6].
The code I have so far is this:
for($i = 0; $i <= count($amount_crystals_color) - 1; $i++)
{
$array = array_fill(0, $amount_crystals_per_color_stack, $crystals_array[$i]);
$i++;
}
Using the above example $amount_crystals_per_color_stack is equal to 2 and amount_crystals_color is equal to 5.
When executing this code it outputs an array: [2,2] which is how many 2's we need, but I can't figure out how to add the remaining crystals to this array.
Can anyone help me out?
Your code has several problems and i will address each of them individually.
Using the for loop to iterate over an array
You are using a for loop in your code, that has the following loop head:
for($i = 0; $i <= count($crystals_array) - 1; $i++)
The loop had consists of three parts, each separated by a semicolon (;).
The first part $i = 0 is the initialization part. Here you initialize a variable, that is later used as an iterator, which shall change in each loop iteration. You could name this the start point as well.
The second part $i <= count($crystals_array) - 1 is the condition part. A condition is formed, that shall express for how long the loop shall iterate. As long as the expression evaluates as true, the loop will run again. Therefore this condition is evaluated at the start of each iteration. As soon as the condition evaluates as false the loop will end. Therefore this part can be named endpoint as well.
The third part $i++ is the step size. This is executed at the end of each iteration and determines how the iterator (the variable you defined in the first part) shall change. $i++ is in this context equal to $i = $i + 1 and represents a step size of 1. Therefore the variable $i gets increased by 1 for each run of the loop.
This said, you can improve and fix your code regarding the for loop with two changes:
Save functions, that are executed in your condition part into an variable, if they return a constant result for each iteration. You use the count() function, which will then count your array again for each iteration of the for loop. By saving it in a variable $count = count($crystals_array); before the for loop and changing the condition to $i < $count, the function is only called once and your code gets faster.
Do not change the iterator variable $i outside of your loop header. This is really bad code style. You added the line $i++; to the end of your loop, but that is already done in the step size part of the for header. Because that is executed at the and of each iteration as well you increased the step size to two, meaning that you only run the for loop with $i = 0, $i = 2 and $i = 4 instead of for each element.
For your code the usage of the $i iterator is only to address the elements of the initial array. Even though you should understand the for loop for the future, you should use a foreach loop for this case instead. The following code would be equivalent to your for loop.
//This code still contains another major bug and is jsut a partial improvvement
foreach($crystals_array as $crystal) {
$array = array_fill(0, $amount_crystals_per_color_stack, $crystal);
}
As you can see, you neither need to worry about counting the initial array, nor in which index the current value is. Instead the variable $crystal will automatically contain the next element for each iteration.
Appending elements to an array
You used the following line to save the newly generated elements in your array:
$array = array_fill(0, $amount_crystals_per_color_stack, $crystal);
If you look closely, you use a standard assignment with $array = at the beginning of your line. This means, that (like with each variable assignment) the previous value of the variable gets overwritten by the new value provided from the right side of the assignment. What you do not want yet is to overwrite the array, but to append something to it.
This can be done by adding two squared brackets to the end of the variable name: $array[] = .... Now, if the variable $array is really an array, what ever value is on the right side of the assignment will be appended to the array, instead of overwriting it.
Managing result types the right way
The following line still contains a major problem:
$array[] = array_fill(0, $amount_crystals_per_color_stack, $crystal);
The result type of array_fill() is an array itself. By appending it to the previous array, you would get the following structure:
$array = [
[2, 2],
[3, 3],
[4, 4],
[5, 5],
[6, 6],
];
As you can see, the code did exactly what it should but not what you wanted. Each result (array) was appended to the array. The result is therefore an array or arrays (or a multidimensional array). What you want instead, is that the values of the result are appended to the existing array.
PHP offers a function for that, named array_merge(). This function takes all elements for one (or more) array(s) and appends them to the end of the first array, that was given to the function. You can use it as followed:
$newCrystals = array_fill(0, $amount_crystals_per_color_stack, $crystal);
$array = array_merge($array, $newCrystals);
As you can see the latter line contains a normal assignment again. ($array =) This is because array_merge() does not modify the first array given to it, but creates a new array with the merged fields. Therefore the new array contains all values from the old one and it is safe to overwrite the old one with it.
The complete code would therefore be:
$array = [];
foreach($crystals_array as $crystal) {
$newCrystals = array_fill(0, $amount_crystals_per_color_stack, $crystal);
$array = array_merge($array, $newCrystals);
}
As I understood the problem
$crystals_array = [2,3,4,5,6];
$amount_crystals_per_color_stack = 2;
$res = [];
foreach($crystals_array as $v) {
// repeat each item from array $amount_crystals_per_color_stack times
$res = array_merge($res, array_fill(0, $amount_crystals_per_color_stack, $v));
}
print_r($res); // [2,2,3,3,4,4,5,5,6,6]
You need to merge your array at each iteration of the loop (repl online) or you lose the result each time.
Like:
$array = array();
for($i = 0; $i < count($amount_crystals_color); $i++)
{
$array = array_merge($array, array_fill(0, $amount_crystals_per_color_stack, $crystals_array[$i]);
}
Also you don't need the $i++ in the loop, because it iterate twice otherwise, and you don't need count(..)-1 if the condition is < instead of <=.
You could use simple foreach() to achieve this-
$amount_crystals_per_color_stack = 2;
$array = [2,3,4,5,6];
$result = array();
foreach($array as $a){
for($i=1;$i<=$amount_crystals_per_color_stack;$i++){
array_push($result, $a);
}
}
print_r($result);
For example i have an array like this [-1,-1,-1,-1,-1,-1,2.5,-1,-1,8.3]
I want to count the element which are not -1 like except of the -1. Is there any function in php to get this ? One approach which i think is
Count the total array - count of the -1 in the array.
how can we achieve this.
P.S : please provide me a comment why this question deserve negative vote.
Like #MarkBaker said, PHP doesn't have a convenient function for every single problem, however, you could make one yourself like this:
$arr = [-1,-1,-1,-1,-1,-1,2.5,-1,-1,8.3];
function countExcludingValuesOfNegativeOne ($arr) {
return count($arr) - array_count_values(array_map('strval', $arr))['-1'];
}
echo countExcludingValuesOfNegativeOne($arr); // Outputs `2`.
It just counts the whole array, then subtracts the number of negative 1s in the array. Because PHP throws an error if any element in the array isn't a string 1 when using array_count_values, I've just converted all elements of the array to a string using array_map('strval', $arr) 2
you can use a for loop counter skipping for a specific number.
function skip_counter($array,$skip){
$counter = 0;
foreach ($array as $value) {
if ($value != $skip) $counter++;
}
return $counter;
}
then you call skip_counter($your_list, $number_to_be_skipped);
Let's say the following is true:
I have an associative array containing an unknown number of elements.
The keys are integers, starting at 1, and each is one more than the last.
There is an element with key N whose value is 1.
The value of each element with a key less than N is 0.
The value of each element with a key greater than N is 1.
This is the array:
The question is :
What is the fastest/smartest way to find the position of the first '1' in the array?
If you truly don't know the length of the array (a very odd situation), then probably all you can do is grow your search geometrically, i.e. skip 4, skip 8, skip 16, etc. until you find a 1, then cut back with a (geometric) binary search.
array_search is your best bet
// Make up some data...
$data = [];
for ($i = 1; $i <= 20; ++$i) {
$data[$i] = rand(0,5);
}
var_dump($data);
// Find the first one...
echo 'The first 1 is at position: ' . array_search(1, $data);
http://php.net/manual/en/function.array-search.php
I have a code that will add a number to an array each time a page is visited. the numbers are stored in a cookie and are retrieved later.
I would like to keep only the 5 most recent numbers in the array.
if the array is full (5 items) and a new number must be added, then the oldest number must be removed and the most recent items must be kept
here's what i have:
$lastviewedarticles = array();
if (isset($_COOKIE["viewed_articles"]) ) {
$lastviewedarticles = unserialize($_COOKIE["viewed_articles"]);
}
if (!in_array($articleid, $lastviewedarticles)){
$lastviewedarticles[] = $articleid;
}
setcookie("viewed_articles", serialize($lastviewedarticles));
array_slice returns a slice of an array
array_slice($array, 0, 5) // return the first five elements
use array_splice and array_unique to get the 5 unique array values
array_splice(array_unique($lastviewedarticles), 0, 5);
First of all i think, you need to obtain array length , then if length > or equal to 5, remove first element , and add element to the end of array.
if (!in_array($articleid, $lastviewedarticles)){
$count = count($lastviewedarticles);
if($count>=5)
array_shift($lastviewedarticles);
$lastviewedarticles[] = $articleid;
}
Use a counter to access the array, increment it in every call and use the modulus operation to write into the array. If your counter has to persist over several calls you have to store it in a session variable or a cookie.
Assuming that $i holds your counter variable this would look like
if (!in_array($articleid, $lastviewedarticles)){
$lastviewedarticles[$i%5] = $articleid;
$i++;
}
The result is a primitive ring buffer that will always contain the last 5 values.
occurrence of A----5 times
occurrence of B----7 times
occurrence of C----6 times
($total['A']=5;
$total['B']=7;
$total['C']=6;)
I need to rate each based on their occurrence as follows,
$rating['A']=3;
$rating['B']=1;//most occurrence will get rate 1.
$rating['C']=2;
asort(&$total);
$rating = 1;
foreach (array_reverse($total) as $key => $val)
$total[$key] = $rating++;
You could also try using the array functions like sorting the values first and get keys of the sorted array and then create another array with the extracted keys as values. Now you get the same array with their rankings, except that you have '0' rank first as arrays start with an index 0.
May be you could pad an additional value with '0' an then finally remove it.
Something like this,
$total['A']=5;
$total['B']=7;
$total['C']=6;
$total[0]=0;
asort($total);
$total = array_slice(array_flip(array_keys($total)),1);
Or if you don't like to pad an extra value, you can try it this way. Create an array with the keys and the count of the sorted array.
asort($total);
$total = array_combine(array_keys($total),range(1, count($total)));
This might be a quick and easy way of doing. Hope this helps.