ABCCBA从1到9不同数字组成算法

$a = Combination(range(0, 9), 3);foreach($a as $v) $r[] = join('', array_merge($v, array_reverse($v)));print_r($r);

Array(    [0] => 789987    [1] => 689986    [2] => 679976    [3] => 678876    [4] => 589985    [5] => 579975    [6] => 578875    [7] => 569965    [8] => 568865    [9] => 567765    [10] => 489984    [11] => 479974    [12] => 478874    [13] => 469964    [14] => 468864    [15] => 467764    [16] => 459954    [17] => 458854    [18] => 457754    [19] => 456654    [20] => 389983    [21] => 379973    [22] => 378873    [23] => 369963    [24] => 368863    [25] => 367763    [26] => 359953    [27] => 358853    [28] => 357753    [29] => 356653    [30] => 349943    [31] => 348843    [32] => 347743    [33] => 346643    [34] => 345543    [35] => 289982    [36] => 279972    [37] => 278872    [38] => 269962    [39] => 268862    [40] => 267762    [41] => 259952    [42] => 258852    [43] => 257752    [44] => 256652    [45] => 249942    [46] => 248842    [47] => 247742    [48] => 246642    [49] => 245542    [50] => 239932    [51] => 238832    [52] => 237732    [53] => 236632    [54] => 235532    [55] => 234432    [56] => 189981    [57] => 179971    [58] => 178871    [59] => 169961    [60] => 168861    [61] => 167761    [62] => 159951    [63] => 158851    [64] => 157751    [65] => 156651    [66] => 149941    [67] => 148841    [68] => 147741    [69] => 146641    [70] => 145541    [71] => 139931    [72] => 138831    [73] => 137731    [74] => 136631    [75] => 135531    [76] => 134431    [77] => 129921    [78] => 128821    [79] => 127721    [80] => 126621    [81] => 125521    [82] => 124421    [83] => 123321    [84] => 089980    [85] => 079970    [86] => 078870    [87] => 069960    [88] => 068860    [89] => 067760    [90] => 059950    [91] => 058850    [92] => 057750    [93] => 056650    [94] => 049940    [95] => 048840    [96] => 047740    [97] => 046640    [98] => 045540    [99] => 039930    [100] => 038830    [101] => 037730    [102] => 036630    [103] => 035530    [104] => 034430    [105] => 029920    [106] => 028820    [107] => 027720    [108] => 026620    [109] => 025520    [110] => 024420    [111] => 023320    [112] => 019910    [113] => 018810    [114] => 017710    [115] => 016610    [116] => 015510    [117] => 014410    [118] => 013310    [119] => 012210)

function Combination( $arr, $num=0) {	$arr = array_values($arr);	$len = count($arr);	if($num == 0) $num = $len;	$res = array();	for($i=1,$n=pow(2, $len); $i<$n; ++$i) {		$tmp = str_pad(base_convert($i, 10, 2), $len, '0', STR_PAD_LEFT);		$t = array();		for($j=0; $j<$len; ++$j) {			if($tmp{$j} == '1') {				$t[] = $arr[$j];			}		}		if(count($t) == $num) $res[] = $t;	}	return $res;  }

for($a=0; $a<10; $a++)  for($b=0; $b<10; $b++)    for($c=0; $c<10; $c++)      if($a != $b && $a != $c && $b != $c) printf("%d%d%d%d%d%d\n", $a, $b, $c, $c, $b, $a);

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