22 lines
584 B
QBasic
22 lines
584 B
QBasic
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10 REM Luhn algorithm - credit card validator - Rosetta Code
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20 DATA "49927398716", 1, "49927398717", 0
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30 DATA "1234567812345670", 1, "1234567812345678", 0
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40 FOR T = 1 TO 4
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50 READ CARD$
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60 S = 0
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70 NDIG = LEN(CARD$)
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80 PARITY = NDIG MOD 2
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90 FOR I = 1 TO NDIG
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100 D = VAL(MID$(CARD$, I, 1))
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110 IF ((I-1) MOD 2) <> PARITY THEN 140
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120 D = D * 2
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130 IF D > 9 THEN D = D - 9
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140 S = S + D
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150 NEXT I
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160 RESULT = 0
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170 IF (S MOD 10) = 0 THEN RESULT = 1
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180 READ EXPECTED
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190 IF RESULT <> EXPECTED THEN PRINT "FAIL: "; CARD$; " sum="; S : END
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200 NEXT T
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210 PRINT "Luhn OK"
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