Network packet processing done!

Oh man, I spent so much time on this, on and off for more than 16 hours.
But it was worth it in the end! Initially I didn't even noticed that there
is a "what to do" part in exercise file, so I started coding following my
own intuition, which wasn't too bad. I felt like I was going places and  passed
a few tests but failed one or two test cases. That's when things started
getting difficult. I tried thinking, paper/pencil, sleeping on it, and reading
forums (coursera, edx has no discussion on this when I worked on it). I
then realized the "what to do" part in exercise and started following it.
I should have stashed my code based on my own intuition, but I didn't. I'm
learning, after all. Then my code got really messy. I added a lot of if
statements and temp variables to get by, but it consistently fails on grader
test case 20. That test case input is from a file, so far I haven't learned
proper way of reading file as input in junit, so I started simplify my code
hoping that I can pass. In the end my code simplification did work and passed
the grader, but I really should learn how to use file input in JUnit, or
how to feed input file. Eclipse makes that easy, but not IDEA, at least not
the version of 2018.2. 2018.3 supposedly has it, but I don't know how to
upgrade it safely on my Manjaro yet.

Woohoo, fun stuff!

1 files changed, 55 insertions, 28 deletions

diff --git a/src/main/NetworkPacket.java b/src/main/NetworkPacket.java
index 805dcf5..7aeea88 100644
--- a/src/main/NetworkPacket.java
+++ b/src/main/NetworkPacket.java
@@ -1,49 +1,76 @@
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Deque;
+import java.util.LinkedList;
 import java.util.Scanner;
 
 public class NetworkPacket {
 
-    public static class Request {
-        public int arrivalTime;
-        public int processTime;
+    static class Request {
+        int arrivalTime;
+        int processTime;
 
-        public Request(int arrivalTime, int processTime) {
+        Request(int arrivalTime, int processTime) {
             this.arrivalTime = arrivalTime;
             this.processTime = processTime;
         }
 
     }
 
-    public static class Response {
-        public boolean dropped;
-        public int startTime;
+    static class Response {
+        boolean dropped;
+        int startTime;
 
-        public Response(boolean dropped, int startTime) {
+        Response(boolean dropped, int startTime) {
             this.dropped = dropped;
             this.startTime = startTime;
         }
     }
 
-    public static class Buffer {
-        private int size;
-        private ArrayList<Integer> finishTime = new ArrayList<Integer>();
+    static class Buffer {
+        private int capacity;
+        private Deque<Integer> finishTime;
 
-        public Buffer(int size) {
-            this.size = size;
+        // My addition to the starter file
+        private int runningTimeCounter = 0;
+        // End of my addition to the starter file
+
+        Buffer(int capacity) {
+            this.capacity = capacity;
+            this.finishTime = new LinkedList<>();
         }
-        public Response processRequests(Request request) {
-            // write your code here
-            if (this.size == 0)
-            return new Response(false,-1);
-            else {
+
+        Response processRequest(Request request) {
+            if (runningTimeCounter < request.arrivalTime)
                 if (finishTime.size() == 0)
+                    runningTimeCounter = request.arrivalTime;
+                else if (finishTime.getLast() < request.arrivalTime)
+                    runningTimeCounter = request.arrivalTime;
+
+            while (finishTime.size() > 0) {
+                int j = finishTime.getFirst();
+                if (j <= request.arrivalTime)
+                    finishTime.pop();
+                else
+                    break;
             }
+
+            if (finishTime.size() >= capacity) {
+                return new Response(true, -1);
+            }
+            Response response = new Response(false, runningTimeCounter);
+            runningTimeCounter = runningTimeCounter + request.processTime;
+            if (finishTime.size() > 0)
+                finishTime.addLast(finishTime.getLast() + request.processTime);
+            else
+                finishTime.addLast(runningTimeCounter);
+            return response;
         }
     }
-    private static ArrayList<Request> ReadQueries(Scanner scanner) throws IOException {
+
+    private static ArrayList<Request> ReadQueries(Scanner scanner) {
         int requests_count = scanner.nextInt();
-        ArrayList<Request> requests = new ArrayList<Request>();
+        ArrayList<Request> requests = new ArrayList<>();
         for (int i = 0; i < requests_count; ++i) {
             int arrival_time = scanner.nextInt();
             int process_time = scanner.nextInt();
@@ -52,16 +79,16 @@ public class NetworkPacket {
         return requests;
     }
 
-    public static ArrayList<Response> processRequests(ArrayList<Request> requests, Buffer buf) {
+    static ArrayList<Response> processRequests(ArrayList<Request> requests, Buffer buf) {
         ArrayList<Response> responses = new ArrayList<>();
-        for (int i = 0; i < requests.size(); i++) {
-           responses.add(buf.processRequests(requests.get(i)));
+        for (Request request : requests) {
+            responses.add(buf.processRequest(request));
         }
         return responses;
     }
+
     private static void PrintResponses(ArrayList<Response> responses) {
-        for (int i = 0; i < responses.size(); ++i) {
-            Response response = responses.get(i);
+        for (Response response : responses) {
             if (response.dropped) {
                 System.out.println(-1);
             } else {
@@ -70,11 +97,11 @@ public class NetworkPacket {
         }
     }
 
-    public static void main(String[] args) throws IOException {
+    public static void main(String[] args) {
         Scanner scanner = new Scanner(System.in);
 
-        int buffer_max_size = scanner.nextInt();
-        Buffer buffer = new Buffer(buffer_max_size);
+        int bufferMaxSize = scanner.nextInt();
+        Buffer buffer = new Buffer(bufferMaxSize);
 
         ArrayList<Request> requests = ReadQueries(scanner);
         ArrayList<Response> responses = processRequests(requests, buffer);