A Collection of Code Snippets in as Many Programming Languages as Possible

This project is maintained by TheRenegadeCoder

Welcome to the Minimum Spanning Tree in Commodore Basic page! Here, you'll find the source code for this program as well as a description of how the program works.

```
10 DIM A(99)
15 REM Graph:
16 REM - G%(i, j, 0) contains vertex index for child node j, vertex i or
17 REM negative to indicate no more child nodes
18 REM - G%(i, j, 1) contains weight between vertex i and child node j
20 DIM G%(9, 10, 1)
25 REM Minimum spanning tree working values
30 DIM MP%(9): REM Parents
40 DIM MK(9): REM Keys
50 DIM MS%(9): REM Set
55 REM Minimum spanning tree output
56 REM - MT(i, 0) contains source vertex index for node i
57 REM - MT(i, 1) contains destination vertex index for node i
58 REM - MT(i, 2) contains weight between source and destination for node i
60 DIM MT%(8, 2)
65 REM Get weights
70 GOSUB 2000
80 IF V = 0 OR C >= 0 THEN GOTO 200: REM invalid or not end of input/value
85 REM Get number of vertices
90 NV = INT(SQR(NA) + 0.5)
100 IF NA <> (NV * NV) THEN GOTO 200: REM non-square input
105 REM Form graph
110 GOSUB 2500
115 REM Perform minimum spanning tree, calculate total weight, and display
120 GOSUB 3000
130 GOSUB 3500
140 S$ = MID$(STR$(TW), 2)
150 PRINT S$
160 END
200 PRINT "Usage: please provide a comma-separated list of integers"
210 END
1000 REM Read input value one character at a time since Commodore BASIC
1001 REM has trouble reading line from stdin properly
1002 REM NR = number
1003 REM V = 1 if valid number, 0 otherwise
1004 REM C = -2 if end of input, -1 if end of value,
1005 REM 32 if whitespace, ASCII code of last character otherwise
1006 REM Initialize
1010 NR = 0
1020 V = 0
1030 S = 1
1035 REM Loop while leading spaces
1040 GOSUB 1500
1050 IF C = 43 OR C = 45 THEN GOTO 1100: REM + or -
1060 IF C >= 48 AND C <= 57 THEN GOTO 1150: REM 0 to 9
1070 IF C = 32 THEN GOTO 1040: REM whitespace
1080 RETURN: REM other character
1085 REM Loop while sign
1090 GOSUB 1500
1100 IF C = 43 THEN GOTO 1090: REM +
1110 IF C >= 48 AND C <= 57 THEN GOTO 1150: REM 0 to 9
1120 IF C <> 45 THEN RETURN: REM not -
1130 S = -S
1140 GOTO 1090
1145 REM Set valid flag
1150 V = 1
1155 REM Loop while digits
1160 NR = (ABS(NR) * 10 + C - 48) * S
1170 GOSUB 1500
1180 IF C >= 48 AND C <= 57 THEN GOTO 1160: REM 0 to 9
1185 REM Loop while trailing spaces
1190 IF C < 0 OR C <> 32 THEN RETURN: REM end character or not whitespace
1200 GOSUB 1500
1210 GOTO 1180
1500 REM Get input character
1501 REM A$ = input character
1502 REM C = One of the following:
1502 REM - -1 if end of value
1503 REM - -2 if end of input
1504 REM - 32 if whitespace
1505 REM - ASCII code otherwise
1510 GET A$
1520 C = ASC(A$)
1530 IF C = 13 THEN C = -1
1540 IF C = 255 THEN C = -2
1550 IF C = 9 OR C = 10 THEN C = 32
1560 RETURN
2000 REM Read array value
2001 REM A contains array value
2002 REM NA contains length of array
2003 REM V = 1 if valid number, 0 otherwise
2004 REM C = -2 if end of input, -1 if end of value,
2005 REM 32 if whitespace, ASCII code of last character otherwise
2006 REM Initialize
2010 NA = 0
2020 GOSUB 1000: REM Read input value
2030 IF V = 0 THEN RETURN: REM invalid
2040 A(NA) = NR
2050 NA = NA + 1
2060 IF C < 0 THEN RETURN: REM end of input or value
2070 IF C = 44 THEN GOTO 2020: REM comma, get next value
2080 V = 0
2090 RETURN
2500 REM Form graph
2501 REM Inputs:
2502 REM - A contains weights
2504 REM - NV contains number of vertices
2505 REM Output: G% contains graph
2510 K = -1
2520 FOR I = 0 TO NV - 1
2530 N = -1
2540 FOR J = 0 TO NV - 1
2550 K = K + 1
2560 IF A(K) <= 0 THEN GOTO 2600
2570 N = N + 1
2580 G%(I, N, 0) = J
2590 G%(I, N, 1) = A(K)
2600 NEXT J
2610 G%(I, N + 1, 0) = -1: REM End of child nodes
2620 G%(I, N + 1, 1) = 0
2630 NEXT I
2640 RETURN
3000 REM Prim's Minimum Spanning Tree (MST) Algorithm based on C
3001 REM implementation of https://www.geeksforgeeks.org/
3002 REM prims-minimum-spanning-tree-mst-greedy-algo-5/
3003 REM Inputs:
3004 REM - G% contains graph
3005 REM - NV contains number of vertices
3006 REM Outputs:
3007 REM - MT contains minimum spanning tree
3008 REM - NM contains size of minimum spanning tree
3010 REM Initialize
3020 FOR I = 0 TO NV - 1
3030 MP%(I) = -1: REM No parents yet
3040 MK(I) = 1.70141183E38: REM Minimum weight edge is infinty
3050 MS%(I) = 0: REM Nothing in MST yet
3060 NEXT I
3065 REM Include first vertex in MST
3070 MK(0) = 0
3075 REM The MST will include all vertices
3080 FOR I = 1 TO NV - 1
3085 REM Pick index of the minimum key value not already in MST
3090 MV = 1.70141183E38: REM Minimum value is infinity
3100 U = -1
3110 FOR J = 0 TO NV - 1
3120 IF MK(J) >= MV OR MS%(J) <> 0 THEN GOTO 3150
3130 MV = MK(J)
3140 U = J
3150 NEXT J
3155 REM Add picked vertex to MST
3160 MS%(U) = 1
3165 REM Update key values and parent indices of picked adjacent vertices.
3166 REM Only consider vertices not yet in MST
3170 J = -1
3180 J = J + 1
3190 V = G%(U, J, 0)
3200 W = G%(U, J, 1)
3210 IF V < 0 THEN GOTO 3260
3220 IF MS%(V) <> 0 OR W >= MK(V) THEN GOTO 3180
3230 MP%(V) = U
3240 MK(V) = W
3250 GOTO 3180
3260 NEXT I
3265 REM Construct MST information to return, skipping over root
3270 NM = NV - 1
3280 FOR I = 1 TO NM
3290 MT(I - 1, 0) = MP%(I)
3300 MT(I - 1, 1) = I
3310 MT(I - 1, 2) = MK(I)
3320 NEXT I
3330 RETURN
3500 REM Calculate total weight of MST
3501 REM Inputs:
3502 REM - MT contains minimum spanning tree
3503 REM - NM contains size of minimum spanning tree
3504 REM Output: TW contains total weight
3510 TW = 0
3520 FOR I = 0 TO NM - 1
3530 TW = TW + MT(I, 2)
3540 NEXT I
3550 RETURN
```

Minimum Spanning Tree in Commodore Basic was written by:

- rzuckerm

If you see anything you'd like to change or update, please consider contributing.

No 'How to Implement the Solution' section available. Please consider contributing.

No 'How to Run the Solution' section available. Please consider contributing.