I am trying to get a range of card type from a list bins that are associated with that card type, but whenever I ran the code the card-type is printed as null am not sure what I am doing wrong
This are the bins in a text
400000000000,499999999999,visa
500000000000,599999999999,mc
400000000000,499999999999,visa
420008000000,420008999999,visadebit
420008000000,435000999999,visa
540008000000,599999999999,mc
Whenever I Pass 4111111111111111 instead of getting visa i end getting null,
this is what I have done so far
package cardsystem;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Scanner;
public class Solution {
/**
* An entity to hold bin range details. A bin range is a pair of 12 digit numbers that
* mark the boundaries of the range which is maped to other bin range properties such
* as a card type. The range boundaries are inclusive.
*/
static final class BinRange {
final String start;
final String end;
final String cardType;
BinRange(String start, String end, String cardType) {
this.start = start;
this.end = end;
this.cardType = cardType;
}
}
// I need a hashmap which hold index and CardType. Each index corresponding an interval (start-end).
private static HashMap<Integer, String> cache = new HashMap<>();
private static List<Long> startEndList = new ArrayList<>();
interface CardTypeCache {
/**
* @param cardNumber 12 to 23 digit card number.
* @return the card type for this cardNumber or null if the card number does not
* fall into any valid bin ranges.
*/
String get(String cardNumber);
}
/**
* @param binRanges the list of card bin ranges to build a cache from.
* @return an implementation of CardTypeCache.
*/
public static CardTypeCache buildCache(List<BinRange> binRanges) {
cache = new HashMap<>();
for (int i = 0; i < binRanges.size(); i++) {
cache.put(i, binRanges.get(i).cardType);
}
for (BinRange binRange : binRanges) {
startEndList.add(Long.valueOf(binRange.start)); // Previously, Integer type used, I converted it to 'Long' type
startEndList.add(Long.valueOf(binRange.end));
}
return new CardTypeCacheImpl();
}
static class CardTypeCacheImpl implements CardTypeCache {
public String get(String cardNumber) {
//Integer index = findIndexLinear(Long.valueOf(cardNumber)); // Linear Search
Integer index = findIndexBinary(Long.valueOf(cardNumber)); // Binary Search
return (index != -1) ? cache.get(index) : "null";
}
/**
* Linear Search O(n)
*
* @param cardNumber, Searching an index which is between start-end .
* @return an index. If not found, return -1.
*/
private Integer findIndexLinear(Long cardNumber) {
for (int i = 1; i < startEndList.size(); i += 2) {
if (startEndList.get(i - 1) <= cardNumber && cardNumber <= startEndList.get(i)) {
return i / 2;
}
}
return -1;
}
/**
* Binary Search O(logn)
*
* @param cardNumber, Searching an index which is between start-end .
* @return an index. If not found, return -1.
*/
private Integer findIndexBinary(Long cardNumber) {
int left = 0;
int right = startEndList.size();
while (left < right) {
int mid = left + (right - left) / 2;
if (mid % 2 == 0 && startEndList.get(mid) <= cardNumber && cardNumber <= startEndList.get(mid + 1)) { // right pair (start-end) of mid
return mid / 2;
} else if (mid % 2 == 1 && startEndList.get(mid - 1) <= cardNumber && cardNumber <= startEndList.get(mid)) { // left pair
return mid / 2;
}
if (cardNumber < startEndList.get(mid)) {
right = mid;
} else {
left = mid + 1;
}
}
return -1;
}
}
public static void main(String[] args) throws IOException {
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(System.out));
File text = new File("D:/dev/CardSystem/src/cardsystem/input.txt");
try (final Scanner scanner = new Scanner(text)) {
List<Solution.BinRange> binRanges = new ArrayList<>();
/*
4111111111111111
400000000000,499999999999,visa
500000000000,599999999999,mc
*/
String cardNumber = scanner.next();
scanner.nextLine();
scanner.useDelimiter("[,\n]");
while (scanner.hasNext()) {
String start = scanner.next();
String end = scanner.next();
String cardType = scanner.next();
binRanges.add(new Solution.BinRange(start, end, cardType));
if (scanner.hasNextLine()) {
scanner.nextLine();
}
}
Solution.CardTypeCache cache = Solution.buildCache(binRanges);
if (cache != null) {
bufferedWriter.write(String.valueOf(cache.get(cardNumber)));
}
}
bufferedWriter.newLine();
bufferedWriter.close();
}
}
What am I doing wrong, been scratching my head for hours
Integer.MAX_VALUEis 2^31 - 1 which is 2,147,483,647. A credit card number doesn't fit in anint. – Stephen CStringto represent credit card numbers. They are not really integers at all. They are identifiers composed of a fixed number of decimal digits. – Stephen Cbyte[]orchar[]in-memory representation that can be erased after use. See Should credit card numbers be stored as strings or ints? – Stephen C