Find the missing permutation: Difference between revisions

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 DBAC is missing</pre>
-=={{header|PHP}}==
-<lang php><?php
-$finalres = Array();
-function permut($arr,$result=array()){
-	global  $finalres;
-	if(empty($arr)){
-		$finalres[] = implode("",$result);
-	}else{
-		foreach($arr as $key => $val){
-			$newArr = $arr;
-			$newres = $result;
-			$newres[] = $val;
-			unset($newArr[$key]);
-			permut($newArr,$newres);
-		}
-	}
-}
-$givenPerms = Array("ABCD","CABD","ACDB","DACB","BCDA","ACBD","ADCB","CDAB","DABC","BCAD","CADB","CDBA","CBAD","ABDC","ADBC","BDCA","DCBA","BACD","BADC","BDAC","CBDA","DBCA","DCAB");
-$given = Array("A","B","C","D");
-permut($given);
-print_r(array_diff($finalres,$givenPerms)); // Array ( [20] => DBAC )
-</lang>
 =={{header|Perl}}==
@@ Line 1,499: / Line 1,477: @@
 <lang perl6>say [~^] @givens;</lang>
 {{out}}<pre>DBAC</pre>
+=={{header|Phix}}==
+<lang Phix>constant perms = {"ABCD", "CABD", "ACDB", "DACB", "BCDA", "ACBD", "ADCB", "CDAB",
+                  "DABC", "BCAD", "CADB", "CDBA", "CBAD", "ABDC", "ADBC", "BDCA",
+                  "DCBA", "BACD", "BADC", "BDAC", "CBDA", "DBCA", "DCAB"}
+-- 1: sum of letters
+sequence r = repeat(0,4)
+for i=1 to length(perms) do
+    r = sq_add(r,perms[i])
+end for
+r = sq_sub(max(r)+'A',r)
+puts(1,r&'\n')
+-- the final step is equivalent to eg {1528,1530,1531,1529}
+--                        max-r[i] -> {   3,   1,   0,   2}
+--                        to chars -> {   D,   B,   A,   C}
+-- (but obviously all done in one step)
+-- 2: the xor trick
+r = repeat(0,4)
+for i=1 to length(perms) do
+    r = sq_xor_bits(r,perms[i])
+end for
+puts(1,r&'\n')
+-- 3: find least frequent letters
+r = "    "
+for i=1 to length(r) do
+    sequence count = repeat(0,4)
+    for j=1 to length(perms) do
+        count[perms[j][i]-'A'+1] += 1
+    end for
+    r[i] = smallest(count,1)+'A'-1
+end for
+puts(1,r&'\n')
+-- 4: test all permutations
+for i=1 to factorial(4) do
+    r = permute(i,"ABCD")
+    if not find(r,perms) then exit end if
+end for
+puts(1,r&'\n')</lang>
+{{out}}
+<pre>
+DBAC
+DBAC
+DBAC
+DBAC
+</pre>
+=={{header|PHP}}==
+<lang php><?php
+$finalres = Array();
+function permut($arr,$result=array()){
+	global  $finalres;
+	if(empty($arr)){
+		$finalres[] = implode("",$result);
+	}else{
+		foreach($arr as $key => $val){
+			$newArr = $arr;
+			$newres = $result;
+			$newres[] = $val;
+			unset($newArr[$key]);
+			permut($newArr,$newres);
+		}
+	}
+}
+$givenPerms = Array("ABCD","CABD","ACDB","DACB","BCDA","ACBD","ADCB","CDAB","DABC","BCAD","CADB","CDBA","CBAD","ABDC","ADBC","BDCA","DCBA","BACD","BADC","BDAC","CBDA","DBCA","DCAB");
+$given = Array("A","B","C","D");
+permut($given);
+print_r(array_diff($finalres,$givenPerms)); // Array ( [20] => DBAC )
+</lang>
 =={{header|PicoLisp}}==