How to get random numbers without repetition in php?

php method to obtain random numbers without duplication: 1. Use the [rand(min,max)] function to generate random numbers; 2. Use [array_unique(arr)] to deduplicate the generated array; 3. Use indexes to quickly generate unique random numbers.

php method to get random numbers without repetition:

The first thing that comes to mind isrand(min, The max) function generates random numbers. In fact, using mt_rand(min,max) can generate random numbers more quickly.

Secondly use array_unique(arr) to deduplicate the generated array. In fact, using array_flip(array_flip(arr)) can deduplicate it more quickly.

Understanding the above two points, we can write a slightly optimized function:

/**
 * 生成指定长度不重复的字符串.
 *
 * @param integer $min 最小值.
 * @param integer $max 最大值.
 * @param integer $len 生成数组长度.
 *
 * @return array
 */
function uniqueRandom($min, $max, $len)
{
    if ($min < 0 || $max < 0 || $len) {
        throw new LogicException(&#39;无效的参数&#39;);
    }
    if ($max <= $min) {
        throw new LogicException(&#39;大小传入错误&#39;);
    }
    $counter = 0;
    $result = array();
    while ($counter < $len) {
        $result[] = mt_rand($min, $max);
        $result = array_flip(array_flip($result));
        $counter = count($result);
    }
    shuffle($result);
    return $result;
}

In fact, you can use the index to generate non-repeating random numbers more quickly, and the efficiency is several times better than the above function. street.

/**
 * 生成指定长度不重复的字符串.
 *
 * @param integer $min 最小值.
 * @param integer $max 最大值.
 * @param integer $len 生成数组长度.
 *
 * @return array
 */
function uniqueRandom2($min, $max, $len)
{
    if ($min < 0 || $max < 0 || $len < 0) {
        throw new LogicException(&#39;无效的参数&#39;);
    }
    if ($max <= $min) {
        throw new LogicException(&#39;大小传入错误&#39;);
    }
    if (($max - $min + 2) < $len) {
        throw new LogicException("传入的范围不足以生成{$len}个不重复的随机数}");
    }
    $index = array();
    for ($i = $min; $i < $max + 1; $i++) {
        $index[$i] = $i;
    }
    $startOne = current($index);
    $endOne = end($index);
    for ($i = $startOne; $i < $endOne; $i++) {
        $one = mt_rand($i, $max);
        if ($index[$i] == $i) {
            $index[$i] = $index[$one];
            $index[$one] = $i;
        }
    }
    return array_slice($index, 0, $len);
}

The ingenuity of this algorithm compared with the above algorithm is:

• Randomizes the self-increasing index, there will be no duplication problems, and it avoids deduplication. Overhead

• Use the array subscript to replace the array itself for randomization. Every time a random number is obtained, it will be excluded from the value range. Next time, it will only be included in the remaining numbers. Fetching, the selection of random numbers can be completed in one traversal.

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