Note to moderators: This is not a homework assignment.
I have the following example:
$points = 10;
$a = 0;
$b = 0;
$c = 0;
$d = 0;
I want to randomly distribute the points to the variables ($a,$b,$c,$d) until $points reach zero. So, expected random output after running some function/script should look like this:
$points = 0;// Must be zero
$a = 3;
$b = 1;
$c = 0;
$d = 6;
I'm thinking of doing a simple solution, which is the following:
while($points > 0) {
$points_taken = mt_rand(0, $points);
$points -= $points_taken;
$a += $points_taken;
$points_taken = mt_rand(0, $points);
$points -= $points_taken;
$b += $points_taken;
$points_taken = mt_rand(0, $points);
$points -= $points_taken;
$c += $points_taken;
$points_taken = mt_rand(0, $points);
$points -= $points_taken;
$d += $points_taken;
}
The function has 1 problem: $a has much more higher chance of taking more points (or even all points) because it's first in the list, while $d has much more higher chance of taking less points (or no points at all) because it's last in the list.
Question: How can I give all variables equal chance of distribution?
Note: It's fine if one of the variables took all the points.
You can use randomly select one of the variables from a range, and assign to it using a variable variable.
$vars = range('a','d');
while ($points) {
$points_taken = mt_rand(0, $points);
$points -= $points_taken;
${$vars[mt_rand(0, 3)]} += $points_taken;
}
Something like this?
$points = 10;
$a = 0;
$b = 0;
$c = 0;
$d = 0;
for($i=0; $i<$points; $i++) {
$rand = rand(1,4);
if($rand == 1) {
$a++;
} else if ($rand == 2) {
$b++;
} else if ($rand == 3) {
$c++;
} else if ($rand == 4) {
$d++;
}
}
Related
I need to get 50 random numbers out of range 1-100 without repeating. The current way i do is :
$array = array();
while (count($array) <= 50) {
$temp = random_int(1,100);
if (!in_array($temp, $array))
$array[] = $temp;
}
However, the looping is too many because I need to generate for more than 100,000 times.
Is there other ways that I can get a 50 random non-repeating numbers without looping ?
For example:
$number= range(1,100);
$array = array_slice(shuffle($number),0,50);
I can't use shuffle because it uses pseudo random number.
Is there other ways to achieve what I need, or ways that could shorten time.
pre fill a array of numbers and pick from them, and then remove it.
it prevents the unnecessary random generations you have
$numbers = [];
for ($i = 1; $i <= 100; $i++) {
$numbers[] = $i;
}
$randomNumbers = [];
for ($i = 1; $i <= 50; $i++) {
$r = rand(0, count($numbers) - 1);
$randomNumbers[] = $numbers[$r];
array_splice($numbers, $r, 1);
}
This would be my approach:
This gives you 50 numbers in any case, and they are defenitely different from each other. PLUS: you dont have to prefill some other array:
$start = microtime(true);
for($i = 0; $i <= 100000; $i++){
$arr = [];
while(sizeof($arr) < 50){
$num = rand(1, 100);
$arr[$num] = $num;
}
if(array_unique($arr) !== $arr || sizeof($arr) !== 50 ){
print("FAIL");
}
//print(array_unique($arr) == $arr ? "true" : "false");print("<br>");
//print(sizeof($arr));print("<br>");
//print_r(array_count_values ($arr));print("<br>");
//print_r($arr);print("<br>");
}
$time_elapsed_secs = microtime(true) - $start;
print($time_elapsed_secs);print("<br>");
Running this 100000 times takes about 0.4sec for me.
The actual generation is done in this part:
$arr = [];
while(sizeof($arr) < 50){
$num = rand(1, 100);
$arr[$num] = $num;
}
We can do in 2 steps:
$x = 0;
$arr = [];
while($x < 50){
$tmp = rand(1, 100);
if(!in_array($tmp, $arr)){
$arr[] = $tmp;
$x++;
}
}
I am working on mathematical problem where the formula is: A[i] * (-2) power of i
where i=0,1,2,3,...
A is an array having values 0 or 1
Input array: [0,1,1,0,0,1,0,1,1,1,0,1,0,1,1]
Output is: 5730
Code
$totalA = 0;
foreach ($A as $i => $a) {
$totalA += $a * pow(-2, $i);
}
This is correct. Now I am looking for its opposite like:
Input is: 5730
Output will be: [0,1,1,0,0,1,0,1,1,1,0,1,0,1,1]
I am not asking for the exact code but looking for some logic from where I should start. I tried to use log() method but that did not return the desired output.
You were not looking for exact code, but I found this problem too interesting. This works:
function sign($n) {
return ($n > 0) - ($n < 0);
}
$target = -2396;
$i = 0;
$currentSum = 0;
// Look for max $i
while (true) {
$val = pow(-2, $i);
$candidate = $currentSum + $val;
if (abs($target) <= abs($candidate)) {
// Found max $i
break;
}
if (abs($target - $candidate) < abs($target - $currentSum)) {
// We are getting closer
$currentSum = $candidate;
}
$i++;
}
$result = [];
for ($j = $i; 0 <= $j; $j--) {
$val = pow(-2, $j);
$border = $val / 4;
if (sign($val) == sign($target) && abs($border) < abs($target)) {
array_unshift($result, 1);
$target -= $val;
} else {
array_unshift($result, 0);
}
}
echo json_encode($result);
First I look for the $i that gets me on or slightly above the $target. When found, I walk down and decide for each bit if it should be in the result.
I use the following to find out the common divisors.
But in some case the count of divisors are not satisfied.
My Code :
$x = 66928;
$y = 66992;
$c_a = [];
$c_b = [];
$d = 1;
while ($d_a <= $x) {
if (is_int($x / $d)) $c_a[] = $d;
$d++;
}
$d = 1;
while ($d_b <= $y) {
if (is_int($y / $d)) $c_b[] = $d;
$d++;
}
echo count($c_a);
echo count($c_b);
// Output
$c_a = 20;
$c_b = 20;
Because, in some cases, it won't work.
Is this type of calculation is right ?
or any suggestions ?
As per asked in comment, to count the common factors of the two no. will be as like this.
<?php
$a = 66928;
$b = 66992;
$min = ($a < $b ) ? $a : $b;
$commomn_factors_count = 0;
for ($i = 1; $i < $min/2; $i++) {
if (($a%$i==0) && ($b%$i==0)) {
$commomn_factors_count++;
}
}
var_dump($commomn_factors_count);
You can you this code to get the fastest result to find the number of common divisors between two numbers:
// Function to calculate gcd of two numbers
function gcd($a, $b)
{
if ($a == 0)
return $b;
return gcd($b % $a, $a);
}
/* Function to calculate all common
* divisors of two given numbers
* a, b --> input integer numbers
*/
function commDiv($a, $b)
{
// find gcd of a, b
$n = gcd($a, $b);
// Count divisors of n.
$result = 0;
for ($i = 1; $i <= sqrt($n);
$i++)
{
// if 'i' is factor of n
if ($n % $i == 0)
{
// check if divisors
// are equal
if ($n / $i == $i)
$result += 1;
else
$result += 2;
}
}
return $result;
}
// Driver Code
$a = 10; $b = 15;
echo(commDiv($a, $b));
The code below will create an array for all possible combination that can occur when you have four different variables. The variables always need to equal 1. The for loops I have created work and I understand how to make this work for more variables, but can I make this dynamic? I need to have a function that has how many variables there are as a parameter. If there are three variables create the three forloops. If there are 10... create the 10 corresponding for loops to determine all possible combinations.
$anarray2 = array();
for( $a = 1; $a <= 97; $a++ ) {
for( $b = 1; $a + $b <=98 ; $b++ ) {
for( $c = 1; $a + $b + $c <= 99; $c++ ) {
$d = 100 - ( $a + $b + $c );
$var_1 = $a / 100;
$var_2 = $b / 100;
$var_3 = $c / 100;
$var_4 = $d / 100;
$anarray2[] = array( $var_1, $var_2, $var_3, $var_4 );
}
}
}
print_array( $anarray2 );
You're effectively looking to share out I identical items to N people in all of the different possible ways.
If there is one person (N==1), then there is only one way to do this - give that person all I items.
If there is more than one person (N>1), then we can consider how many items can be assigned to the first person, and then what the possible assignments are for the remaining N-1 people in each case.
This leads to a nice recursive solution. Firstly we solve the problem for N=1:
function assign($I, $N) {
$anarray = array();
if ($N == 1) {
$anarray[] = array($I);
} else {
// Coming up...
}
return $anarray;
}
Now we solve the problem for N=k (some constant) in terms of N=k-1 - that is, we solve the problem using the solution to a smaller problem. This will reach all the way back to the solution when N=1.
function assign($I, $N) {
$anarray = array();
if ($N == 1) {
$anarray[] = array($I);
} else {
for ($i = $I; $i < $I; $i++) {
foreach (assign($I - $i, $N - 1) as $subproblem) {
$anarray[] = array_merge(array($i), $subproblem);
}
}
}
return $anarray;
}
Something like that should do the job.
I am trying to create a function which maps a recurring pattern of integers using an array.
As an example if I have a starting array of (0,1,3) and I know that I want to stop the pattern when I hit 15.
The pattern gets incremented by a fixed integer each time (lets say 4) so my final pattern should be..
0
1
3
4 (0 + 4)
5 (1 + 4)
7 (2 + 4)
8 (4 + 4)
9 (5 + 4)
11(7 + 4)
12(8 + 4)
13(9 + 4)
15(11+ 4)
Does anyone have any pointers on how this can be achieved?
My current implementation works but is stupidly inefficient which something like this...
$array = array(0,1,3);
$inc = 4;
$end = end($array);
$final = 15;
while($end < $final)
{
$tmp = array();
foreach($array AS $row)
{
$tmp = $row + $inc;
}
$array = merge($tmp, $array);
$end = end($array);
}
$array = array(0,1,3);
$inc = 4;
$final = 15;
$end = end($array);
while($end < $final)
{
$end += $inc;
$array[] = $end;
}
Or with a for loop:
$array = array(0,1,3);
$inc = 4;
$final = 15;
for($i = end($array) + $inc; $i <= $final; $i += $inc)
{
$array[] = $i;
}
Y'all are missing the fact that 4 is being added to the value in the array 2 keys back, not the last value.
This is the code you need (tested, and working)
$array = array(0,1,3);
$inc = 4;
$end = end($array);
$key = key($array);
$final = 15;
while ($end < $final) {
if ($array[$key-2] >= 0) {
$end = $array[$key-2] + $inc;
$array[] = $end;
$key++;
}
}
I also included in there a check to make sure the key being added to actually exists, though that may not be needed.
I assume that you want to have all the new values in the same array.
So:
//original array
$values = array(0, 1, 3);
//incremental value
$inc = 4;
//stop value
$stop = 15;
//set the index counter to the origin
$curr_index = 0;
//while the last value of the array is lower than the stop value
while($values[end($values)] < $stop)
{
//calculate the new value
$new_value = $values[$curr_index] + $inc;
//add the new value to the array
array_push($values, $new_value);
//update the index counter
$curr_index ++;
}
this code should work for any initial value in the array, any incremental value and any stop value.
<?php
function myArrayFunction(array $array, $inc = 4, $final = 15, $end = null)
{
if(!$end)
{
$end = end($array);
}
while($end < $final)
{
$end += $inc;
$array[] = $end;
}
return $array; //assume you're wanting $array back
}
This is minus any sort of testing or checking of injected values but you get the idea.
It would be better to know what you are trying to achieve here as the whole thing looks horribly overcomplicated, but...
$array = array(0,1,3);
$pattern = array();
$inc = 4;
$final = 15;
for ($base = 0; ; $base += $inc) {
foreach($array as $rem) {
if ($base + $rem > $final) break 2;
$pattern []= $base + $rem;
}
}
Alternatively,
$i = $v = 0;
while ($v < $final) {
$v = $pattern []= $pattern[$i++] + $inc;
}
(This assumes $final will be part of the pattern.)
If you can figure out how to calculate the number of elements will be in the array beforehand and assign that to $tum this should work.
<?php
$arr = array(0, 1, 3);
$inc = 4; // 6
$fin = 15; // 55
$num = count($arr);
$lum = 0;
$tum = 12; // 29
do
{
for($i = $lum; $i < $num; $i++)
{
$tar = $arr[$i] + $inc;
$arr[$tar] = $tar;
}
$lum = $num;
$num *= 2;
} while(end($arr) < $fin);
$arr = array_slice($arr, 0, $tum);
print_r($arr);
echo "\n";
?>