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

This project is maintained by TheRenegadeCoder

Welcome to the Binary Search 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)
20 GOSUB 2000: REM Get array
30 IF V = 0 OR C <> -1 THEN GOTO 200: REM invalid or end of input/value
40 GOSUB 1000: REM Get target value
50 IF V = 0 OR C >= 0 THEN GOTO 200: REM invalid or not end of input/value
60 GOSUB 2500: REM Check if sorted
70 IF V = 0 THEN GOTO 200: REM not sorted
75 REM Perform binary search
80 T = NR
90 GOSUB 3000
100 R$ = "false"
110 IF I >= 0 THEN R$ = "true"
120 PRINT R$
130 END
200 Q$ = CHR$(34): REM quote
210 PRINT "Usage: please provide a list of sorted integers ";
220 PRINT "("; Q$; "1, 4, 5, 11, 12"; Q$; ") and the integer to find ";
230 PRINT "("; Q$; "11"; Q$; ")"
240 END
1000 REM Read input value one character at a time since Commodore BASIC
1001 REM has trouble reading line from stdin properly
1002 REM NR = number
1003 REM V = 1 if valid number, 0 otherwise
1004 REM C = -2 if end of input, -1 if end of value,
1005 REM 32 if whitespace, ASCII code of last character otherwise
1006 REM Initialize
1010 NR = 0
1020 V = 0
1030 S = 1
1035 REM Loop while leading spaces
1040 GOSUB 1500
1050 IF C = 43 OR C = 45 THEN GOTO 1100: REM + or -
1060 IF C >= 48 AND C <= 57 THEN GOTO 1150: REM 0 to 9
1070 IF C = 32 THEN GOTO 1040: REM whitespace
1080 RETURN: REM other character
1085 REM Loop while sign
1090 GOSUB 1500
1100 IF C = 43 THEN GOTO 1090: REM +
1110 IF C >= 48 AND C <= 57 THEN GOTO 1150: REM 0 to 9
1120 IF C <> 45 THEN RETURN: REM not -
1130 S = -S
1140 GOTO 1090
1145 REM Set valid flag
1150 V = 1
1155 REM Loop while digits
1160 NR = (ABS(NR) * 10 + C - 48) * S
1170 GOSUB 1500
1180 IF C >= 48 AND C <= 57 THEN GOTO 1160: REM 0 to 9
1185 REM Loop while trailing spaces
1190 IF C < 0 OR C <> 32 THEN RETURN: REM end character or not whitespace
1200 GOSUB 1500
1210 GOTO 1180
1500 REM Get input character
1501 REM A$ = 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 Check if sorted
2502 REM - A contains array to search
2503 REM - NA contains size of array
2504 REM Outputs: V = 1 if sorted, 0 otherwise
2510 I = -1
2520 V = 1
2530 I = I + 1
2540 IF I >= (NA - 1) THEN RETURN
2550 IF A(I) > A(I + 1) THEN V = 0: RETURN: REM Not sorted
2560 GOTO 2530
3000 REM Binary search
3001 REM Inputs:
3002 REM - A contains array to search
3003 REM - NA contains size of array
3004 REM - T contains item to find
3005 REM Outputs: I contains index of array item found, -1 if not found
3010 I = -1
3020 LO = 0
3030 HI = NA - 1
3040 IF LO > HI THEN I = -1: RETURN: REM Not found
3050 MD = INT((LO + HI) / 2)
3060 IF A(MD) = T THEN I = MD: RETURN: REM Found
3070 IF A(MD) < T THEN LO = MD + 1: REM Too low, move lower bound
3080 IF A(MD) > T THEN HI = MD - 1: REM Too high, move upper bound
3090 GOTO 3040
```

Binary Search 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.