100 O$ = "A" : T$ = "EF"
110 DEF FN N(P) = ASC(MID$(N$,P+(P=0),1))-64
120 DIM D(26),UNVISITED(26)
130 DIM PREVIOUS(26) : TRUE = 1
140 LET M = -1 : INFINITY = M
150 FOR I = 0 TO 26
160     LET D(I) = INFINITY : NEXT
170 FOR NE = M TO 1E38 STEP .5
180     READ C$
190     IF LEN(C$) THEN NEXT
200 DIM C(NE),FROM(NE),T(NE)
210 DIM PC(NE) : RESTORE
220 FOR I = 0 TO NE
230     READ C(I), N$
240     LET FROM(I) = FN N(1)
250     LET UNVISITED(FR(I)) = TRUE
260     LET T(I) = FN N(3)
270     LET UNVISITED(T(I)) = TRUE
290 NEXT
300 N$ = O$ : O = FN N(0)
310 D(O) = 0
320 FOR CV = O TO EMPTY STEP 0
330     FOR I = 0 TO NE
340         IF FROM(I) = CV THEN N = T(I) : D = D(CV) + C(I) : IF (D(N) = INFINITY) OR (D < D(N)) THEN D(N) = D : PREVIOUS(N) = CV : PC(N) = C(I)
350     NEXT I
360     LET UNVISITED(CV) = FALSE
370     LET MV =  EMPTY
380     FOR I = 1 TO 26
390         IF UNVISITED(I) THEN MD = D(MV) * (MV <> INFINITY) + INFINITY * (MV = INFINITY) : IF (D(I) <> INFINITY) AND ((MD = INFINITY) OR (D(I) < MD)) THEN MV = I
400     NEXT I
410     LET CV = MV * (MD <> INF)
420 NEXT CV : M$ = CHR$(13)
430 PRINT "SHORTEST PATH";
440 FOR I = 1 TO LEN(T$)
450     LET N$ = MID$(T$, I, 1)
460     PRINT M$ "    FROM " O$;
470     PRINT " TO "; : N = FN N(0)
480     IF D(N) = INFINITY THEN PRINT N$" DOES NOT EXIST.";
490     IF D(N) <> INFINITY THEN FOR N = N TO FALSE STEP 0 : PRINT CHR$(N + 64); : IF N <  > O THEN  PRINT " <- "; : N = PREVIOUS(N): NEXT N
500     IF D(N) <> INFINITY THEN PRINT : PRINT "      IS "; : N = FN N(0) : PRINT D(N); : H = 15 : FOR N = N TO O STEP 0: IF N <  > O THEN  P = PREVIOUS(N): PRINT TAB(H)CHR$(43+18*(h=15));TAB(H+2)PC(N); :N = P: H=H+5: NEXT N
510 NEXT I
600 DATA  7,A-B
610 DATA  9,A-C
620 DATA 14,A-F
630 DATA 10,B-C
640 DATA 15,B-D
650 DATA 11,C-D
660 DATA  2,C-F
670 DATA  6,D-E
680 DATA  9,E-F
690 DATA