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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Array ( [0] => 43 [1] => 16 [2] => 15 [3] => 30 [4] => 21 [5] => 1 [6] => 51 [7] => 19 [8] => 2 [9] => 13 [10] => 0 [11] => 33 [12] => 47 [13] => 12 [14] => 10 [15] => 50 [16] => 14 [17] => 35 [18] => 39 [19] => 34 [20] => 31 [21] => 27 [22] => 17 [23] => 38 [24] => 11 [25] => 5 [26] => 4 [27] => 41 [28] => 26 [29] => 37 [30] => 25 [31] => 53 [32] => 9 [33] => 3 [34] => 18 [35] => 42 [36] => 20 [37] => 44 [38] => 6 [39] => 49 [40] => 23 [41] => 28 [42] => 40 [43] => 8 [44] => 45 [45] => 48 [46] => 22 [47] => 7 [48] => 36 [49] => 46 [50] => 32 [51] => 24 [52] => 29 [53] => 52 )
