	PROGRAM MAZE
	COMMON L(64,64),MS,KM,N(4096)
	DATA NR1,NR2,KM/0,0,0/
	LOGICAL*1 LR(64,64)
C
10	TYPE 1000
	ACCEPT 1010,NCELL
	IF(NCELL.LT.2.OR.NCELL.GT.63)GO TO 10
1000	FORMAT(1H0,'HOW MAY CELLS PER SIDE?'$)
1010	FORMAT(I5)
	MS=4090/NCELL
	NSIDE=MS*NCELL
C
	TYPE 1020
	ACCEPT 1010,NR
1020	FORMAT(1H ,'RANDOM NUMBER PLEASE:',$)
	NR=ABS(NR)+200
	DO 20,I=1,NR
20	X=RAN(NR1,NR2)
C
	TYPE 1030
	ACCEPT 1010,NSPD
	CALL PLOT(9,NSPD,15)
	CALL PLOT(2,-2047,-2047)
1030	FORMAT(1H ,'WHAT SPEED?',$)
C
	TYPE 1040
	ACCEPT 1050,RAND
1040	FORMAT(1H0,'RANDOM THRESHOLD(0.0 TO 1.0)?',$)
1050	FORMAT(F6.0)
C
	DO 30,I=1,64
	DO 30,J=1,64
30	L(I,J)=0
	DO 32,I=1,NCELL+1
	L(I,1)=1
32	L(I,NCELL+1)=1
	DO 34,J=2,NCELL
	L(1,J)=1
34	L(NCELL+1,J)=1
	DO 36,I=1,4096
36	N(I)=0
	NM=2
	KM=0
	CELLM=NCELL-1
	IM=NCELL+1
	JM=NCELL+1
	DO 40,I=1,64
	DO 40,J=1,64
40	LR(I,J)=.FALSE.
C
	JEXIT=NCELL*RAN(NR1,NR2)+1
	JSTART=NCELL*RAN(NR1,NR2)+1
	CALL PLOT(0)
	CALL PLOT(8,-2048,2047,-2048,2047)
	CALL PLOT(3,0,0)
	CALL PLOT(5,NSIDE,0)
	CALL PLOT(5,NSIDE,(JEXIT-1)*MS)
	CALL PLOT(3,NSIDE,JEXIT*MS)
	CALL PLOT(5,NSIDE,NSIDE)
	CALL PLOT(5,0,NSIDE)
	CALL PLOT(5,0,JSTART*MS)
	CALL PLOT(3,0,(JSTART-1)*MS)
	CALL PLOT(5,0,0)
C
C	Preparations Over Now.
C	Draw Horizontal Lines
C
	DO 200,J=2,JM-1				!Over rows
	CALL PLOT(3,0,(J-1)*MS)
	DO 200,I=2,IM				!Over colums
	IF(RAN(NR1,NR2).GT.RAND) GO TO 170	!Random skip
	IF(I.EQ.2) GO TO 130
	IF(I.EQ.IM) GO TO 140			!RHS?
	IF(L(I-1,J).EQ.0) GO TO 150		!New Line
	L(I,J)=L(I-1,J)
	GO TO 190
130	L(I,J)=1				!LHS
	GO TO 190
140	IF(L(I-1,J).NE.0) GO TO 145		!RHS
	L(I-1,J)=1
	GO TO 190
145	IF(L(I-1,J).EQ.1) GO TO 170
	N(L(I-1,J))=1				!Old line, attach
	GO TO 190
150	L(I-1,J)=NM
	L(I,J)=NM
	NM=NM+1
	GO TO 190
170	CALL PLOT(3,(I-1)*MS,(J-1)*MS)	!Skip
	GO TO 200
190	CALL PLOT(5,(I-1)*MS,(J-1)*MS)	!Draw
200	CONTINUE
C
C	Horizontal Lines Done
C	Draw Vertical Lines
C
	DO 300,IX=2,IM-1
	DO 300,JX=2,JM
205	I=CELLM*RAN(NR1,NR2)+2
	J=NCELL*RAN(NR1,NR2)+2
	IF(LR(I,J))GO TO 205
	LR(I,J)=.TRUE.
	NHI=TRACE(I,J)
	NLO=TRACE(I,J-1)
	IF(NLO.GT.1)GO TO 240			!n,x?
	IF(NLO.EQ.1)GO TO 220			!1,x
	IF(NHI.EQ.0) GO TO 210			!0,0?
	CALL DRAW(I,J,NHI,I,J-1)		!0,1/n draw
	GO TO 300
210	CALL DRAW(I,J,NM,I,J)			!0,0 Draw
	L(I,J-1)=L(I,J)
	NM=NM+1
	GO TO 300
220	IF(NHI.EQ.1) GO TO 300			!1,1 Skip
	IF(NHI.EQ.0)GO TO 230			!1,0?
	N(NHI)=1
225	CALL PLOT(3,(I-1)*MS,(J-2)*MS)
	CALL PLOT(5,(I-1)*MS,(J-1)*MS)
	GO TO 300
230	CALL DRAW(I,J,1,I,J)			!1,0
	GO TO 300				!1,x all Done
240	IF(NHI.EQ.NLO) GO TO 300		!n,=n Skip
	IF(NHI.GT.1) GO TO 260			!n,n?
	IF(NHI.EQ.1) GO TO 250			!n,1?
	CALL DRAW(I,J,NLO,I,J)			!n,0
	GO TO 300
250	N(NLO)=1				!n,1
	GO TO 225
260	M=MAX0(NHI,NLO)				!n,n
	N(M)=MIN0(NHI,NLO)
	GO TO 225				!n,x all done
300	CONTINUE
	TYPE 1100,NM,KM
D	TYPE 1110,((L(I,J),I=1,IM),J=1,JM)
1100	FORMAT(1H ,'NM REACHED',I4,'  KM REACHED',I4)
1110	FORMAT(1H ,15I4)
	CALL PLOT(1)
	GO TO 10
	STOP
	END
C
C
	FUNCTION TRACE(I,J)
	DIMENSION NSAV(200)
	COMMON L(64,64),MS,KM,N(4096)
	NT=L(I,J)
	IF(NT.LT.2) GO TO 50
	DO 10,K=1,200
	NSAV(K)=NT
	IF(NT.GT.4095) GO TO 60
	NT=N(NT)
	IF(NT.LT.2) GO TO 12
10	CONTINUE
	TYPE 1000,(NSAV(K),K=1,200)
1000	FORMAT(1H0,10I6)
	PAUSE 'FAILURE! KM>200'
12	IF(NT.EQ.0) GO TO 20
D	DO 15,KL=1,K			!Attached: reassign all
D15	N(NSAV(KL))=1			!to 1. NT=1
	GO TO 50
20	IF(K.GT.1) GO TO 30		!Not attached
	NT=NSAV(1)			!Only 1 linkage. NT=n
	GO TO 50
30	CONTINUE
D	DO 35,KL=1,K-1			!Several links.  Reassign
D35	N(NSAV(KL))=NSAV(K)		!All to root n
	NT=NSAV(K)
50	TRACE=NT
	IF(K.GT.KM)KM=K
	RETURN
60	TYPE 1010,NT,I,J
1010	FORMAT(1X,'NT=',I6,' AT I,J=',I3,','I3)
	STOP
	END
C
C
	SUBROUTINE DRAW(I,J,N,IN,JN)
	COMMON L(64,64),MS
	CALL PLOT(3,(I-1)*MS,(J-2)*MS)	!Draw from below to
	CALL PLOT(5,(I-1)*MS,(J-1)*MS)	!Point I,J
	L(IN,JN)=N				!Attach line number to a point
	RETURN
	END
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