One Pay - Karat Interview (rejected)

One Pay

Karat Round

Was broadly asked 2 questions which were easy enough but the question was too convoluted to understand the context and answer in a short while. Was given less than 40 minutes.

The first question given was to correct the code to pass the test cases. It was mostly a data type fix, the timestamp was a string initially, after changing it to float, the test cases worked.

Second question was to write a function to count the total journey of all the users. The interview ended before I could complete the function.

import static org.junit.Assert.assertEquals;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;

/*
We are writing software to analyze logs for toll booths on a highway. This highway is a divided highway with limited access; the only way on to or off of the highway is through a toll booth.

There are three types of toll booths:
* ENTRY (E in the diagram) toll booths, where a car goes through a booth as it enters the highway.
* EXIT (X in the diagram) toll booths, where a car goes through a booth as it exits the highway.
* MAINROAD (M in the diagram), which have sensors that record a license plate as a car drives through at full speed.

        Exit Booth                         Entry Booth
            |                                   |
            X                                   E
             \                                 /
---<------------<---------M---------<-----------<---------<----
                                         (West-bound side)

===============================================================

                                         (East-bound side)
------>--------->---------M--------->--------->--------->------
             /                                 \
            E                                   X
            |                                   |
        Entry Booth                         Exit Booth
*/
/*
We are interested in how many people are using the highway, and so we would like to count how many complete journeys are taken in the log file.

A complete journey consists of:
* A driver entering the highway through an ENTRY toll booth.
* The driver passing through some number of MAINROAD toll booths (possibly 0).
* The driver exiting the highway through an EXIT toll booth.

For example, the following excerpt of log lines contains complete journeys for the cars with JOX304 and THX138:

.
.
.
90750.191 JOX304 250E ENTRY
91081.684 JOX304 260E MAINROAD
91082.101 THX138 110E ENTRY
91483.251 JOX304 270E MAINROAD
91873.920 THX138 120E MAINROAD
91874.493 JOX304 280E EXIT
.
.
91982.102 THX138 290E EXIT
92301.302 THX138 300E ENTRY
92371.302 THX138 310E EXIT
.

*/

2-1) Write a function in LogFile named countJourneys() that returns how many
     complete journeys there are in the given LogFile.
*/

class LogEntry {

/**

• Represents an entry from a single log line. Log lines look like this in the file:
• 34400.409 SXY288 210E ENTRY
• Where:
• • 34400.409 is the timestamp in seconds since the software was started.
• • SXY288 is the license plate of the vehicle passing through the toll booth.
• • 210E is the location and traffic direction of the toll booth. Here, the toll
• booth is at 210 kilometers from the start of the tollway, and the E indicates
• that the toll booth was on the east-bound traffic side. Tollbooths are placed
• every ten kilometers.
• • ENTRY indicates which type of toll booth the vehicle went through. This is one of
• "ENTRY", "EXIT", or "MAINROAD". **/

private final float timestamp; private final String licensePlate; private final String boothType; private final int location; private final String direction;

public LogEntry(String logLine) { String[] tokens = logLine.split(" "); this.timestamp = Float.parseFloat(tokens[0]); this.licensePlate = tokens[1]; this.boothType = tokens[3]; this.location = Integer.parseInt(tokens[2].substring(0, tokens[2].length() - 1)); String directionLetter = tokens[2].substring(tokens[2].length() - 1); if (directionLetter.equals("E")) { this.direction = "EAST"; } else if (directionLetter.equals("W")) { this.direction = "WEST"; } else { throw new IllegalArgumentException(); } }

public float getTimestamp() { return timestamp; }

public String getLicensePlate() { return licensePlate; }

public String getBoothType() { return boothType; }

public int getLocation() { return location; }

public String getDirection() { return direction; }

@Override public String toString() { return String.format( "<LogEntry timestamp: %f license: %s location: %d direction: %s booth type: %s>", timestamp, licensePlate, location, direction, boothType ); } }

class LogFile {

/*

• Represents a file containing a number of log lines, converted to LogEntry
• objects. */

List logEntries;

public LogFile(BufferedReader reader) throws IOException { this.logEntries = new ArrayList<>(); String line = reader.readLine(); while (line != null) { LogEntry logEntry = new LogEntry(line.strip()); this.logEntries.add(logEntry); line = reader.readLine(); } }

// // HashMap<>(); // entry Hashmap // { // "JOX304" -> "1", // "THX138" -> "2", // }

// exit Hashmap // { // "Jox" -> 1, //
// "THX138" -> "2", //
// }

public int countJourneys() { Map<String, Integer> entryMap = new HashMap<>(); Map<String, Integer> exitMap = new HashMap<>();

for(LogEntry singleLog: this.logEntries) {
  String singleBoothType = singleLog.getBoothType();
  String licensePlate = singleLog.getLicensePlate();
  
  if(singleBoothType == "ENTRY") {
    
    entryMap.put(licensePlate, entryMap.getOrDefault(licensePlate, 0) + 1);
  } else if(singleBoothType == "EXIT") {
    exitMap.put(licensePlate, entryMap.getOrDefault(licensePlate, 0) + 1);
  }
}

int totalCount = 0;
for(Map.Entry<String, Integer> entry : entryMap.entrySet()) {
  
  String singleLicensePlate = entry.getKey();
  int count = entry.getValue();
  
  if(exitMap.containsKey(singleLicensePlate)) {
    totalCount += exitMap.get(singleLicensePlate);
  }
}

return totalCount;

}

public LogEntry get(int index) { return this.logEntries.get(index); }

public int size() { return this.logEntries.size(); } }

public class Solution {

public static void main(String[] argv) throws IOException { System.out.println("executing main"); testLogFile(); testLogEntry(); testCountJourneys(); }

public static void testLogFile() throws IOException { System.out.println("Running testLogFile"); try ( BufferedReader reader = new BufferedReader( new FileReader("/content/test/tollbooth_small.log") ); ) { LogFile logFile = new LogFile(reader); assertEquals(13, logFile.size()); for (LogEntry entry : logFile.logEntries) { assert (entry instanceof LogEntry); } } }

public static void testLogEntry() { System.out.println("Running testLogEntry"); String logLine = "44776.619 KTB918 310E MAINROAD"; LogEntry logEntry = new LogEntry(logLine);

System.out.println("line 166");
System.out.printf("timestamp is %s\n", logEntry.getTimestamp());
assertEquals(44776.619f, logEntry.getTimestamp(), 0.0001);
assertEquals("KTB918", logEntry.getLicensePlate());
assertEquals(310, logEntry.getLocation());
assertEquals("EAST", logEntry.getDirection());
assertEquals("MAINROAD", logEntry.getBoothType());
logLine = "52160.132 ABC123 400W ENTRY";
logEntry = new LogEntry(logLine);
assertEquals(52160.132f, logEntry.getTimestamp(), 0.0001);
assertEquals("ABC123", logEntry.getLicensePlate());
assertEquals(400, logEntry.getLocation());
assertEquals("WEST", logEntry.getDirection());
assertEquals("ENTRY", logEntry.getBoothType());

}

public static void testCountJourneys() throws IOException {
System.out.println("Running testCountJourneys");
try (BufferedReader reader = new BufferedReader(new FileReader("/content/test/tollbooth_small.log"))) {
    LogFile logFile = new LogFile(reader);
    assertEquals(3, logFile.countJourneys());
}

try (BufferedReader reader = new BufferedReader(new FileReader("/content/test/tollbooth_medium.log"))) {
    LogFile logFile = new LogFile(reader);
    assertEquals(63, logFile.countJourneys());
}

} }