1 <?php 2 #洗牌算法，假设共有n张各不相同的牌 3 #易知n张牌共有n!中排列方法，洗牌算法关键在于让这n！排列方法出现的概率相等 4 5 function swap(&$arr, $i, $j) { 6 $temp = $arr[$i]; 7 $arr[$i] = $arr[$j]; 8 $arr[$j] = $temp; 9 } 10 11 function shuffle_poker(&$arr) { 12 $len = count($arr); 13 for ($i = 0; $i < $len; $i++) { 14 $j = rand() % ($len - $i) + $i; #关键部分，每次选取rand() % (n - i) + i的一张牌和i交换 15 swap($arr, $i, $j); 16 } 17 } 18 19 for ($i = 0; $i < 54; $i++) { 20 $arr[] = $i; 21 } 22 23 print_r($arr); 24 25 echo "<br>"; 26 27 shuffle_poker($arr); 28 29 print_r($arr); 30 ?>
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