i need to generate random UNIQUE numbers within a range ? how to do ?
i can generate randoms number by
generator: $arr=array(); $x=rand($min,$max); $len=count($arr); $flag = 0; for($i=0;$iI know this code is bad, so i need a better optimized code of my version ! help !
example: if i need to generate 3 numbers within 1 to 15 they should be like 5, 9, 1 but not 3,1,2 [with in 1 - 3 (numbers i want to generate) ]
Array with range of numbers at random order:
$numbers = range(1, 20); shuffle($numbers); Wrapped function:
function UniqueRandomNumbersWithinRange($min, $max, $quantity) { $numbers = range($min, $max); shuffle($numbers); return array_slice($numbers, 0, $quantity); } Example:
Result:
Array ( [0] => 14 [1] => 16 [2] => 17 [3] => 20 [4] => 1 ) $len = 10; // total number of numbers $min = 100; // minimum $max = 999; // maximum $range = []; // initialize array foreach (range(0, $len - 1) as $i) { while(in_array($num = mt_rand($min, $max), $range)); $range[] = $num; } print_r($range); I was interested to see how the accepted answer stacks up against mine. It's useful to note, a hybrid of both may be advantageous; in fact a function that conditionally uses one or the other depending on certain values:
# The accepted answer function randRange1($min, $max, $count) { $numbers = range($min, $max); shuffle($numbers); return array_slice($numbers, 0, $count); } # My answer function randRange2($min, $max, $count) { $range = array(); while ($i++ The results:
randRange1: small range, high count 0.019910097122192 randRange2: small range, high count 1.5043621063232 randRange1: high range, small count 2.4722430706024 randRange2: high range, small count 0.0001051425933837 If you're using a smaller range and a higher count of returned values, the accepted answer is certainly optimal; however as I had expected, larger ranges and smaller counts will take much longer with the accepted answer, as it must store every possible value in range. You even run the risk of blowing PHP's memory cap. A hybrid that evaluates the ratio between range and count, and conditionally chooses the generator would be the best of both worlds.
The idea consists to use the keys, when a value is already present in the array keys, the array size stays the same:
function getDistinctRandomNumbers ($nb, $min, $max) { if ($max - $min + 1 Pro: This way avoids the use of in_array and doesn't generate a huge array. So, it is fast and preserves a lot of memory.
Cons: when the rate (range/quantity) decreases, the speed decreases too (but stays correct). For a same rate, relative speed increases with the range size.(*)
(*) I understand that fact since there are more free integers to select (in particular for the first steps), but if somebody has the mathematical formula that describes this behaviour, I am interested by, don't hesitate.
Conclusion: The best "general" function seems to be a mix between this function and @Anne function that is more efficient with a little rate. This function should switch between the two ways when a certain quantity is needed and a rate (range/quantity) is reached. So the complexity/time of the test to know that, must be taken in account.
If you want to generate 100 numbers that are random, but each number appearing only once, a good way would be to generate an array with the numbers in order, then shuffle it.
Something like this:
$arr = array(); for ($i=1;$iOutput will look something like this:
Array ( [0] => 16 [1] => 93 [2] => 46 [3] => 55 [4] => 18 [5] => 63 [6] => 19 [7] => 91 [8] => 99 [9] => 14 [10] => 45 [11] => 68 [12] => 61 [13] => 86 [14] => 64 [15] => 17 [16] => 27 [17] => 35 [18] => 87 [19] => 10 [20] => 95 [21] => 43 [22] => 51 [23] => 92 [24] => 22 [25] => 58 [26] => 71 [27] => 13 [28] => 66 [29] => 53 [30] => 49 [31] => 78 [32] => 69 [33] => 1 [34] => 42 [35] => 47 [36] => 26 [37] => 76 [38] => 70 [39] => 100 [40] => 57 [41] => 2 [42] => 23 [43] => 15 [44] => 96 [45] => 48 [46] => 29 [47] => 81 [48] => 4 [49] => 33 [50] => 79 [51] => 84 [52] => 80 [53] => 101 [54] => 88 [55] => 90 [56] => 56 [57] => 62 [58] => 65 [59] => 38 [60] => 67 [61] => 74 [62] => 37 [63] => 60 [64] => 21 [65] => 89 [66] => 3 [67] => 32 [68] => 25 [69] => 52 [70] => 50 [71] => 20 [72] => 12 [73] => 7 [74] => 54 [75] => 36 [76] => 28 [77] => 97 [78] => 94 [79] => 41 [80] => 72 [81] => 40 [82] => 83 [83] => 30 [84] => 34 [85] => 39 [86] => 6 [87] => 98 [88] => 8 [89] => 24 [90] => 5 [91] => 11 [92] => 73 [93] => 44 [94] => 85 [95] => 82 [96] => 75 [97] => 31 [98] => 77 [99] => 9 [100] => 59 ) If you need 5 random numbers between 1 and 15, you should do:
var_dump(getRandomNumbers(1, 15, 5)); function getRandomNumbers($min, $max, $count) { if ($count > (($max - $min)+1)) { return false; } $values = range($min, $max); shuffle($values); return array_slice($values,0, $count); } It will return false if you specify a count value larger then the possible range of numbers.
You can try next code:
function unique_randoms($min, $max, $count) { $arr = array(); while(count($arr) Get a random number. Is it stored in the array already? If not, store it. If so, then go get another random number and repeat.
I guess this is probably a non issue for most but I tried to solve it. I think I have a pretty decent solution. In case anyone else stumbles upon this issue.
function randomNums($gen, $trim, $low, $high) { $results_to_gen = $gen; $low_range = $low; $high_range = $high; $trim_results_to= $trim; $items = array(); $results = range( 1, $results_to_gen); $i = 1; foreach($results as $result) { $result = mt_rand( $low_range, $high_range); $items[] = $result; } $unique = array_unique( $items, SORT_NUMERIC); $countem = count( $unique); $unique_counted = $countem -$trim_results_to; $sum = array_slice($unique, $unique_counted); foreach ($sum as $key) { $output = $i++.' : '.$key.'
'; echo $output; } } randomNums(1100, 1000 ,890000, 899999);
This probably will solve your problem:
This is how I would do it.
$randnum1 = mt_rand(1,20); $nomatch = 0; while($nomatch == 0){ $randnum2 = mt_rand(1,20); if($randnum2 != $randnum1){ $nomatch = 1; } } $nomatch = 0; while($nomatch == 0){ $randnum3 = mt_rand(1,20); if(($randnum3 != $randnum1)and($randnum3 != $randnum2)){ $nomatch = 1; } } Then you can echo the results to check
echo "Random numbers are " . $randnum1 . "," . $randnum2 . ", and " . $randnum3 . "\n"; The "shuffle" method has a MAJOR FALW. When the numbers are big, shuffle 3 billion indexs will instantly CAUSE 500 error. Here comes a best solution for really big numbers.
function getRandomNumbers($min, $max, $total) { $temp_arr = array(); while(sizeof($temp_arr) Say I want to get 10 unique random numbers from 1 billion to 4 billion.
$random_numbers = getRandomNumbers(1000000000,4000000000,10); PS: Execution time: 0.027 microseconds
Simply use this function and pass the count of number you want to generate
Code:
function randomFix($length) { $random= ""; srand((double)microtime()*1000000); $data = "AbcDE123IJKLMN67QRSTUVWXYZ"; $data .= "aBCdefghijklmn123opq45rs67tuv89wxyz"; $data .= "0FGH45OP89"; for($i = 0; $i The best way to generate the unique random number is