Data commit

Task/Permutations-by-swapping/QBasic/permutations-by-swapping.basic

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+SUB perms (n)
+    DIM p((n + 1) * 4)
+    FOR i = 1 TO n
+    p(i) = -i
+    NEXT i
+    s = 1
+
+    DO
+    PRINT "Perm: (";
+    FOR i = 1 TO n
+        PRINT ABS(p(i)); "";
+    NEXT i
+    PRINT ") Sign: "; s
+
+    k = 0
+    FOR i = 2 TO n
+        IF p(i) < 0 AND (ABS(p(i)) > ABS(p(i - 1))) AND (ABS(p(i)) > ABS(p(k))) THEN k = i
+    NEXT i
+    FOR i = 1 TO n - 1
+        IF p(i) > 0 AND (ABS(p(i)) > ABS(p(i + 1))) AND (ABS(p(i)) > ABS(p(k))) THEN k = i
+    NEXT i
+    IF k THEN
+        FOR i = 1 TO n    'reverse elements > k
+        IF ABS(p(i)) > ABS(p(k)) THEN p(i) = -p(i)
+        NEXT i
+        'if p(k) < 0 then i = k-1 else i = k+1
+        i = k + SGN(p(k))
+        SWAP p(k), p(i)
+        'temp = p(k)
+        'p(k) = p(i)
+        'p(i) = temp
+        s = -s
+    END IF
+    LOOP UNTIL k = 0
+END SUB
+
+perms (3)
+PRINT
+perms (4)