PHP full-array Recursive algorithm code

function rank ($base, $temp =null) { $len = strlen ($base); if ($len <= 1) { echo $temp. $base. ' '; } Else { for ($i =0; $i < $len; + + $i) { Rank (substr ($base, 0, $i). substr ($base, $i +1, $len-$i-1), $temp. $base [$i]); } } } Rank (' 123 '); ?> Copy Code However, after several tests of the results of the operation, it was found that there was a problem: if the same element exists, then the whole permutation is repeated. For example, there are only three cases of the full arrangement of ' 122 ': ' 122 ', ' 212 ', ' 221 '; Slightly modified, add a judge to repeat the logo, problem solving. function Fsrank ($base, $temp =null) { Static $ret = Array (); $len = strlen ($base); if ($len <= 1) { echo $temp. $base. ' '; $ret [] = $temp. $base; } Else { for ($i =0; $i < $len; + + $i) { $had _flag = false; for ($j =0; $j < $i; + + $j) { if ($base [$i] = = $base [$j]) { $had _flag = true; Break } } if ($had _flag) { Continue } Fsrank (substr ($base, 0, $i). substr ($base, $i +1, $len-$i-1), $temp. $base [$i]); } } return $ret; } print ' '; Print_r (Fsrank (' 122 ')); print ' '; ?> Copy CodeThis paper introduces the recursive algorithm of the whole arrangement, here we recommend a full array of PHP arrays of non-recursive algorithm implementation code, we can refer to the next.

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