不在数组中的随机数[重复]

Question

This question is an exact duplicate of:

• PHP how to get a random number that is different from values of an array 1 answer

I have an array of numbers and I need to make a random number then check if that number is not in the array, If it is make another random number and then check that number to see if its in the array.

example.

array = 1, 2, 4, 5, 7
rand(1, 7) = 3 or 6

if rand(1, 7) = 1, 2, 4, 5 or 7 it would run again until it returned 3 or 6.

anyone know how to do this in php?

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Answer 1

You may simply generate a random number and check if it is already in the array

$in = [1, 4, 7, 9];
do {
    $rand = rand($min, $max);
} while(in_array($rand, $in));

echo $rand, ' is random, but not in the input array';

The above code generates a random integer that is insides the bounds defined in $min and $max. If the value already exists inside the array a new random value is fetched and compared to the input array.

Note: While the above is the minimal working code you may create an endless loop if your input array contains all possible values(Thanks @Action Dan). You didn't state in your question whether this is possible or not. If it is possible you need to work around this. Either by limiting the the maximum tries or validating the input array before and issuing an error message or increasing the 2nd parameter of rand.

Example(validating, only recommended for smaller arrays):

$in = [1,2,3,4,5];
$min = 1;
$max = 5;
if(range($min, $max) === $in) {
    echo 'No possible value in range';
    exit;
}
// code from above