How to compare every value in a for loop? - php

I have a multidimentional array of 5 items and I want that my loop would compare it like:
1 -> 2, 1 -> 3, 1 -> 4, 1 -> 5, 2->1, 2->3, 2->4, 2->5......// so on and 5 -> 4 in the end.
The problem is that after my array $i value matches 1 and $j value matches 3, the unset is done and the $i value becomes 2 (which is correct) and $j value becomes 4 instead of 3. Could someone tell me why and what I'm doing wrong?
My loop is:
for ($i = 0; $i <= count($myArray); $i++) {
for ($j = $i+1; $j <= count($myArray); $j++) {
if (
// condition 1
&& // condition 2
) {
unset($myArray[$i]);
$i++;
}
}
}

I think that's the problem is when you unset the element in the array, you increment the counter of the loop $i. In this way, the elements of the array that are not configured are removed, this empty array position will be maintained, it will not be reordered, you will have to do it manually or using array_values ​​method.
In the last tour of the array, it will break because you are comparing the number of array elements as equal. You must use index < count($array)
The code would be like this:
for ($i = 0; $i < count($myArray); $i++) {
for ($j = $i+1; $j < count($myArray); $j++) {
if (
// condition 1
&& // condition 2
) {
unset($myArray[$i]);
// $i++;
}
}
}

try something like this
for ($i = 0; $i <= count($myArray); $i++) {
for ($j = 0; $j <= count($myArray); $j++) {
if ($j!=$i)
{
if (
// condition 1
&& // condition 2
) {
unset($myArray[$i]);
$i++;
}
}
}
}

$temp = $myArray;
for ($i = 0; $i <= count($myArray); $i++)
{
for ($j = $i + 1; $j <= count($myArray); $j++)
{
if (
// condition 1
&& // condition 2
)
{
unset($temp[$i]);
$i++;
}
}
}
print_r($temp);
Your result is in $temp. So here indexes wont get hampered, you actually are applying all operation on $temp and normally traversing $myArray.

To be honest, I do not know why nobody has yet advise to use nested foreach, since you all noticed there was a problem with array size.
foreach ($numbers as $number_horizontal_parsing) {
foreach ($numbers as $number_vertical_parsing) {
if ($number_horizontal_parsing != $number_vertical_parsing) {
//do your stuff in your case it seems you want to compare both variables
}
}
}

Related

Combining and Permuting items of two different arrays in PHP

How do I return all possible combinations [12345], [12354] up to [54312], [54321] without having to run 120 for...loop as in the case of combining a 2-item array in the code below?
To return all possible combinations from the given array $word = [1,2],
//break the array into 2 separate arrays
$arr1 = $word[0]; $arr2 = $word[1];
//computer for first array item...each item will have 2 loops
for($i=0; $i<count($arr1); $i++){
for($j=0; $j<count($arr2); $j++){
$ret = $arr1[$i] . $arr2[$j]; array_push($result, $ret);
}
}
//computer for second array item..each item will have 2 loops
for($i=0; $i<count($arr2); $i++){
for($j=0; $j<count($arr1); $j++){
$ret = $arr2[$i] . $arr1[$j]; array_push($result, $ret);
}
}
//display the result
for ($i = 0; $i < count($result); $i++){
echo result([$i];
}
The above code works well.
But for a 5-item array [1,2,3,4,5], it will require about (5 items * 24 loops) = 120 loops.
As seen, you wanted to split 2 strings into chars and obtain all combination by 2 chars: first form blank1 and second from blank2.
Instead of doing the combination manually use a regular for-loop.
$result = array();
for ($i = 0; $i < count($blank1); $i++)
{
for ($j = 0; $j < count($blank2); $j++)
{
//set combination
$aux = $blank1[$i].$blank2[$j];
array_push($result, $aux);
}
}
//result should be populated with combination of 2
//just list it and use as need
for ($i = 0; $i < count($result); $i++)
{
echo $result[$i];
}
//same with stored or checking on db : use loops
For multiple combination, use more nested loops
eg: [blank1][blank2][blank1] - 3 combination
$result = array();
//1
for ($i = 0; $i < count($blank1); $i++)
{
//2
for ($j = 0; $j < count($blank2); $j++)
{
//3
for ($k = 0; $k < count($blank1); $k++)
{
//set combination
$aux = $blank1[$i].$blank2[$j].$blank1[$k];
array_push($result, $aux);
}
}
}
Same as any number you wanted ! It will be a little annoying if have to write many loops but note while can be used with an adequate algorithm. But for the moment just keep as simple as you can and get the desired result.

For loop (php) that results in this: 12345678910987654321

My niece is trying to create one for-loop (php), that results in this:
* 12345678910987654321
example for loop she tried:
for ($i = 1; $i <= 10; $i++ , $i = 10; $i <= 1; $i--) {
echo $i . ' ';
}
She can only use if's and elseif's. I'm not a programmer and can't really help her. Any ideas how this could be achieved in php?
Any information would be greatly appreciated.
The key is to add a variable instead of a number, then reverse that number when $i hits 10.
for($i = 1, $j = 1; $i> 0; $i+=$j) // Start i at 1, and j at 1
{
echo $i;
if($i == 10)
$j = -1; // i has hit 10, so use -1 to start subtracting
}
Another possibility is to loop up to 20, printing $i for the ascending part and 20 - $i for the descending.
for ($i = 1; $i < 20; $i++) {
if ($i <= 10) {
echo $i;
} else {
echo 20 - $i;
}
}

loop error in php code

Here is my code, and it is not removing $arr[5] element so that I am trying to remove strings starting with # from my array
this is code
<?php
$arr = [
'#EXTM3U',
'#EXTINF:177,Paul Dateh & Oren Yoel - Be More',
'Be More.mp3',
'#EXTINF:291,Christopher Toy - Just Because',
'Just Because.mp3',
'#EXTINF:238,Magnetic North - Drift Away',
'Drift Away.mp3'
];
for ($i = 0; $i <= count($arr); $i++) {
if ($arr[$i]{0} == '#') {
echo $arr[$i] . "\n";
unset($arr[$i]);
}
}
print_r($arr);
?>
Reason:- You are counting array length inside the loop and every time when any value got unset() from the array, length of array decreased and value of count($array) changed (simply decreased)
So logically your 5th and 6th element never goes through if condition (they never get traversed by loop because of decreasing length of the array )
Solution 1:- Put count outside and it will work properly:-
$count = count($arr);
//loop start from 0 so use < only otherwise, sometime you will get an undefined index error
for ($i = 0; $i < $count; $i++) {
if ($arr[$i]{0} == '#') {
//echo $arr[$i] . "\n";
unset($arr[$i]);
}
}
print_r($arr);
Output:-https://eval.in/996494
Solution 2:- That's why i prefer foreach() over for() loop
foreach($arr as $key=> $ar){
if ($ar[0] == '#') {
unset($arr[$key]);
}
}
print_r($arr);
Output:-https://eval.in/996502
more spacific :
for ($i = 0; $i < count($arr); $i++) {
if (strpos($arr[$i], '#') !== false) {
echo "<br/>";
} else {
echo $arr[$i]."<br/>";
}
}
Try to use additional array to push right values. You calc count($arr); each iteration and when you do count($arr); your array gets smaller and count($arr); returns smaller values, so last elements won't be comparing, try to use variable to calc count before loop make changes:
<?php
//...
$start_count = count($arr);
for ($i = 0; $i <= $start_count; $i++) {
if ($arr[$i]{0} == '#') {
echo $arr[$i] . "\n";
unset($arr[$i]);
}
}
Or remove bad element with a help of additional array, put good elements in new array and don't delete them from input array:
<?php
$arr = [
'#EXTM3U',
'#EXTINF:177,Paul Dateh & Oren Yoel - Be More',
'Be More.mp3',
'#EXTINF:291,Christopher Toy - Just Because',
'Just Because.mp3',
'#EXTINF:238,Magnetic North - Drift Away',
'Drift Away.mp3'
];
$cleared_from_mess_array = array();
for ($i = 0; $i <= count($arr); $i++) {
if ($arr[$i]{0} != '#')
{
array_push($cleared_from_mess_array,$arr[$i]);
}
}
print_r($cleared_from_mess_array);
exit;

Change variable value and push it after loop

I have code like this
$jumlahcolspan = array();//new array
$horizontaldeep = 5;
$level = array(5,4,3,8,7);//old array
for ($j = 0; $j < $horizontaldeep; $j++) {
$jml = 1;
for ($i = $j + 1; $i < $horizontaldeep; $i++) {
$jml = $level[$i] * $jml;
}
array_push($jumlahcolspan, $jml);
}
To put it simple, what I want to get is to multiply old array value which index start from $i+1 to the last and push it to another array.
So, its some thing like this
old array: [5, 4, 3, 8, 7]
new array: [4*3*8*7, 3*8*7, 7, 1]
I've tried this but it doesn't work also
for ($j = 0; $j < $horizontaldeep; $j++) {
$jml = 1;
for ($i = $j + 1; $i < $horizontaldeep; $i++) {
global $jml;
$jml = $level[$i] * $jml;
}
array_push($jumlahcolspan, $jml);
}
Tried this too but not work also.
for ($j = 0; $j < $horizontaldeep; $j++) {
array_push($jumlahcolspan, array_product(array_slice($level, $j+1)));
}
Note: now I'm reviewing my full code. May be something not right in my code.
I think the problem is related to $jml variable but I can't figure how to solve that. Can anyone help me?
One approach would be to use a Recursive Function to achieve that goal. The Recursive Function below demonstrates how. And, by the way, you may as well quick-test it here.
<?php
$oldArray = [5,4,3,8,7];
function arrayMatrixMultiply(array $old, array &$newArray=[]){
$result = 1;
foreach($old as $key=>$value){
if($key != 0){
$result*=$value;
}
}
$newArray[] = $result;
array_splice($old, 0, 1);
if(!empty($old)){
// JUST RECURSE TILL THE $oldArray BECOMES EMPTY
arrayMatrixMultiply($old, $newArray);
}
return $newArray;
}
$newArray = arrayMatrixMultiply($oldArray);
var_dump($newArray);
// PRODUCES::
array (size=5)
0 => int 672
1 => int 168
2 => int 56
3 => int 7

php array output problem

In php is there a function to increment the
values of subsequent values twice(*2) in an array
column based on an initial value?
$beta = array(
array('5', '1''1','1','1','1','1','1','1','1','1','1','1','1','1','1','1','1','1','1'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2'),
array('5','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2','2')
);
/*Example: '5' will be '10' (5*2 =10 and output 10 to web)
'2' will be '4' (2*2 = 4 and output 4 to web)
The next '2' will be '16' (4*2 = 8 and output 8 to web)
The next '2' will be '32' (8*2 = 16 and output 16 to web)
And so forth? */
Furthermore is there an easier way to construct this array, cause I firmly believe there is, but not something too complicated in terms of construct such that a noob will not understand it, again thanks.
[Disclaimer: I have spent 3 days trying to understand arrays, I now understand them; however, I am still new and am currently having some issues when trying to manipulate the values in my array and output them to the web.And I am still pretty sure I have a lot to read and learn, so please no flamers, I just need some help, found this problem in this C++ book:
[http://books.google.com/books?id=4Fn_P7tdOZgC&pg=PT424&lpg=PT424&dq=subsequent+++column+is+twice+the+value&source=bl&ots=gSvQ_LhxoI&sig=dG_Ilf1iLO86lqX936cT1PpkPc8&hl=en&ei=OEEBS_eODYyotgOFtJD3CQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAgQ6AEwAA#v=onepage&q=subsequent%20%20%20column%20is%20twice%20the%20value&f=false][1]
You can try array_map:
<?php
function increase($n) {
return is_array($n) ? array_map('increase', $n) : $n * 2;
}
$new_beta = array_map("increase", $beta);
As for constructing the array, there are other methods to do so but I believe this is the most performent and clean.
Here is an answer for each question in that section of the book, enjoy!
<?php
// Declare an array alpha of 10 rows and 20 columns of type int
// Initialise the array alpha to 0
$alpha = array(array());
for($i = 0; $i < 10; $i++)
{
for($j = 0; $j < 20; $j++)
{
$alpha[$i][$j] = 0;
}
}
// Store 1 in the first row and 2 in the remaining rows
for($i = 0; $i < 10; $i++)
{
for($j = 0; $j < 20; $j++)
{
if($i == 0)
{
$alpha[$i][$j] = 1;
}
else
{
$alpha[$i][$j] = 2;
}
}
}
// Store 5 in the first column, and make sure that the value in
// each subsequent column is twice the value in the previous column
// (Beware this doesn't build off the initial value of 5 in the first
// column but the previously set values above)
for($i = 0; $i < 10; $i++)
{
for($j = 0; $j < 20; $j++)
{
if($j == 0)
{
$alpha[$i][$j] = 5;
}
else
{
if($j - 1 >= 1)
{
$alpha[$i][$j] = $alpha[$i][$j-1] * 2;
}
}
}
}
// Print the array alpha one row per line
print "Printing the array alpha one row per line:<br/>";
for($i = 0; $i < 10; $i++)
{
for($j = 0; $j < 20; $j++)
{
print "[". $alpha[$i][$j] ."] ";
}
print "<br/>";
}
print "<br/>";
// Print the array alpha one column per line
print "Printing the array alpha one column per line:<br/>";
for($j = 0; $j < 20; $j++)
{
for($i = 0; $i < 10; $i++)
{
print "[". $alpha[$i][$j] ."] ";
}
print "<br/>";
}
?>

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