RANDOMIZE
PRINT
PRINT "１〜ｎの自然数をランダムに並べます。"
PRINT
INPUT PROMPT "ｎ＝？ ":n
PRINT
DIM a(n),b(n)
PRINT
FOR i=1 TO n
   LET a(i)=i
   LET b(i)=i
   PRINT a(i);
NEXT i
PRINT
PRINT
CALL shuffle(a,n)
PRINT
FOR j=1 TO n
   PRINT b(j);
NEXT j
PRINT
PRINT "            ↓↓"
FOR j=1 TO n
   PRINT a(j);
NEXT j
PRINT
PRINT
END

EXTERNAL SUB shuffle(a(),n)      !シャッフルする
FOR i=n TO 2 STEP -1
   LET p=INT(RND*(i-1))+1 !左側 1〜i-1
   PRINT "ランダム";i-1;"以下の数字 p =";p
   PRINT "a(";i;") =";a(i);"   a(";p;") =";a(p)
   PRINT
   IF i>2 THEN
      LET t=a(i) !右端iと交換する
      LET a(i)=a(p)
      LET a(p)=t
      
      FOR j=1 TO n
         PRINT a(j);
      NEXT j
      PRINT
      PRINT
   ELSE
      IF RND<0.5 THEN
         LET t=a(i) !右端iと交換する
         LET a(i)=a(1)
         LET a(1)=t
         PRINT "RND < 0.5 なので"
         FOR j=1 TO n
            PRINT a(j);
         NEXT j
         PRINT
         PRINT
      ELSE
         PRINT "RND >= 0.5 なので"
         FOR j=1 TO n
            PRINT a(j);
         NEXT j
         PRINT
         PRINT
      END IF
   END IF
NEXT i
END SUB