Final Version

gsd-questions.tex

@@ -1,10 +1,15 @@
-\documentclass[a4paper,11pt]{article}
+\documentclass[a4paper,10pt]{article}
 
+\usepackage{a4wide}
+\usepackage{german}
+\usepackage{graphicx}
+\usepackage{versions}
 \usepackage{amsmath}
 \usepackage{color}
 \usepackage{colortbl}
 \usepackage{anysize}
 \usepackage{enumerate}
+\usepackage{verbatim}
 
 \usepackage[utf8]{inputenc}
 \usepackage{amssymb}
@@ -16,13 +21,163 @@
 \setlength{\parindent}{0mm}
 
 \begin{document}
+\vspace*{-3cm}
+\hspace*{-1cm}\begin{tabular}{p{.55\linewidth}p{.55\linewidth}}
+  \begin{minipage}{\linewidth}
+    {\bf Global Software Development} \\
+    Kreiker, Pape, Rieger, Todtenh"ofer\\
+    Summer Term 2018\\\\
+    \today\\
+  \end{minipage}
+  &
+  \includegraphics[width=\linewidth]{images/logo}
+\end{tabular}
+
+\begin{center}
+  {\Large\bf GSD Interview Questions}\\
+\end{center}
+
 %\def\loesung{}
-\textsc{Hochschule Fulda}{\small\hfill GSD Database \& SQL questionnaire}\\
-{\small Fachbereich Angewandte Informatik{\small\hfill SS 18}\\
-Dipl.-Inf. Christian Pape}\\
 
+\section{Programming}
+\subsection{Row Vectors}
+Consider an $n\times m$ matrix. Calculate the absolute value for each row vector of the matrix in a programming language of your choice. Example:
+$$
+\left(\begin{array}{cc}
+  2 & 2 \\ 4 & 4 \\ 6 & 5
+\end{array}\right)
+\qquad \Rightarrow \qquad\texttt{calcAbsRowVector}\qquad \Rightarrow \qquad
+\left(\begin{array}{c}
+  2.82 \\ 5.65 \\ 7.81
+\end{array}\right)
+$$
+
+\subsection{Merging and Sorting}
+Let $A$ and $B$ be two arrays of $n$ (unsorted) integer entries each. Write
+a function that merges both arrays into a \emph{sorted} array of $2\dot n$
+entries. Example:
+$$
+\begin{array}{lcl}
+  A & = & [2, 7, 5, 34]\\
+  B & = & [3, 48, 4, 72]\\
+  \hline
+  C & = & [2, 3, 4, 5, 7, 34, 48, 72]\\
+\end{array}
+$$
+
+
+\subsection{Recursion}
+
+Consider a herd of cows. Write a \emph{recursive} function to calculate the
+sum of all legs. Use addition only (no multiplication allowed).
+
+\ifdefined\loesung
+\subsection{Loesung}
+\verbatiminput{todten/GSDSolution.java}
+\fi
+
+\section{Algorithms and Data Structures}
+
+\subsection{In-situ List Reversal}
+Describe an algorithm to reverse a singly-linked list that \emph{does not}
+copy any memory cells.
+
+\ifdefined\loesung
+\textcolor{red}{
+    {\bf Solution}: Maintain three pointers following each other: current, next, and
+    previous. The first pointer is one element ahead of the second. Reverse each pointer
+    as you you.}
+\fi
+
+\subsection{Preorder Tree Traversal}
+Consider the following tree and state the \emph{preorder} and \emph{inorder} traversal.
+\begin{verbatim}
+     5
+   /   \
+  7     4
+   \   / \
+    1 2   9
+\end{verbatim}
+Which data structure do you need to implement such a traversal?
+\ifdefined\loesung
+\textcolor{red}{
+    {\bf Solution}: Preorder: 5, 7, 1, 4, 2, 9; Inorder: 7, 1, 5, 2, 4, 9.
+    Such traversals are implemented using a stack (explicitly or implicitly using
+    a recursive traversal)}
+\fi
+
+\subsection{Breadth-First-Search}
+What is the BFS traversal of the tree above? Which data structure is needed to implement
+such a traversal?
+\ifdefined\loesung
+\textcolor{red}{
+    {\bf Solution}: BFS: 5, 7, 4, 1, 2, 9. You need a queue to implement BFS.}
+\fi
+
+\section{Networking}
+\subsection{Protocol Stacks}
+Explain the major differences between the network protocols UDP, TCP and IP.
+
+\ifdefined\loesung
+\textcolor{red}{
+	{\bf Solution}: UDP is connectionless, offers no error correction etc., data is sent directly without handshake, typically used for real-time protocols. TCP is connection-oriented, offers error correction, flow control (also congestion control), bidirectional reliable data transfer. IP is on a different layer (Layer 3 / network layer) compared to TCP and UDP (Layer 4 / transport layer), IP is connectionless transports datagrams between endpoints, supports routing etc.}
+\fi
+
+\subsection{TCP Characteristics}
+Fill the gaps with appropriate values for the corresponding TCP header fields:
+
+\begin{figure}[htb]
+	\includegraphics[width=0.9\columnwidth]{images/tcp-handshake-and-flowcontrol.png}
+\end{figure}
+
+\ifdefined\loesung
+\textcolor{red}{
+	{\bf Solution}: 2: Flags = SYN+ACK, 3: Flags = ACK, 5: ACK = sa+900, Data-Length = 400 (according to ACK in 7), 6: SEQ = sa+900, Data-Length = 100 (due to limit in (Receive) Window Size), 7: sa+1000.}
+\fi
+
+\subsection{Network Addresses}
+Insert the Layer 2 and Layer 3 addresses used the following transfer from Computer A to Computer B. How many IP addresses can exist in the subnet Computer B is placed in? What is the network address of this subnet?
+
+\begin{figure}[htb]
+	\includegraphics[width=0.9\columnwidth]{images/mac-address.png}
+\end{figure}
+
+\ifdefined\loesung
+\textcolor{red}{
+	{\bf Solution}: Source IP: 1.1.1.10 (not 1.1.1.10/24), Destination IP: 2.2.15.100 (not 2.2.15.100/21), Source MAC: 11:22:33:44:55:66, Destination MAC: aa:bb:cc:dd:ee:ff (not 33:44:55:66:77:88). Number of hosts in /21 IPv4 subnet = 2046 ($2^{32-21}-2$). Network address of the IP subnet of Computer B: 2.2.8.0/21.}
+\fi
+
+\section{Regular Expressions and Shells}
+\subsection{Regular Expression}
+Explain the following regex:
+\begin{verbatim}
+^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$
+\end{verbatim}
+
+\ifdefined\loesung
+\textcolor{red}{
+  {\bf Solution}: This regex describes well-formatted IPv4 addresses. Number of repetitions
+  given in braces, Question mark for optional choices, brackets denote ranges.}
+\fi
+
+\subsection{Extract Lines}
+Write a shell command to extract lines number 101-110 from a file {\tt a.txt} and
+output them (numerically sorted) to file {\tt b.txt}.
+\ifdefined\loesung\textcolor{red}{
+  {\bf Solution}: {\tt cat a.txt | head -110 | tail -10 | sort -n > b.txt}}
+\fi
+
+\subsection{Large Files}
+Write a shell command to find the file with the most number of lines in
+the current directory.
+\ifdefined\loesung\textcolor{red}{
+  {\bf Solution}: {\tt wc -l * | sort -nr} is key. One might get rid of the \emph{total} line count
+  and access the file name only. Optional.}
+\fi
+
+\section{Databases}
 %------------------------------------------------------------------------------
-\textbf{Task 1 (SQL statements):}\\
+\subsection{SQL statements}
 %------------------------------------------------------------------------------
 Write down the results of the following SQL statements on table T.
 \begin{quote}
@@ -102,13 +257,8 @@ T & A & B & C \\
   \end{quote}
 \end{description}
 
-\pagebreak
-\textsc{Hochschule Fulda}{\small\hfill GSD Database \& SQL questionnaire}\\
-{\small Fachbereich Angewandte Informatik{\small\hfill SS 18}\\
-Dipl.-Inf. Christian Pape}\\
-
 %------------------------------------------------------------------------------
-\textbf{Task 2 (constraints \& integrity):}\\
+\subsection{Constraints \& Integrity}
 %------------------------------------------------------------------------------
 The following table definition with integrity constraints are given.
 \begin{quote}
@@ -175,13 +325,8 @@ Nr. & INSERT-statement & Violated constraint \\[0.3cm]
 \hline
 \end{tabular}
 
-\pagebreak
-\textsc{Hochschule Fulda}{\small\hfill GSD Database \& SQL questionnaire}\\
-{\small Fachbereich Angewandte Informatik{\small\hfill SS 18}\\
-Dipl.-Inf. Christian Pape}\\
-
 %------------------------------------------------------------------------------
-\textbf{Task 3 (relations \& DDL-statements):}\\
+\subsection{Relations \& DDL-statements}
 %------------------------------------------------------------------------------
 The following tables and DDL-statements are given. Please note: an exam with a grade other than 5.0 is passed.
 \begin{figure}[htb]
@@ -194,8 +339,6 @@ The following tables and DDL-statements are given. Please note: an exam with a g
   \end{minipage}
 \end{figure}
 
-
- 
 \begin{description}
   \item[a.)] What is defined in the table {\tt STUDENT}?
   \ifdefined\loesung \textcolor{red}{

todten/GSDSolution.java

@@ -0,0 +1,111 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package gsdsolution;
+
+/**
+ *
+ * @author todten
+ */
+import java.math.*;
+import java.util.*;
+
+public class GSDSolution {
+
+    /* Main Program */
+    public static void main(String[] args) {
+        
+        int someCows = 10;
+
+        System.out.println(someCows + " cows have " + countLegs(someCows) + " legs \n");
+
+        System.out.println("Calculate Row Vector");
+        calcAbsRowVector(inputMatrix);
+        
+        System.out.println("Merge and Sort Arrays");
+        mergeAndSortArrays(input1, input2);
+
+    }
+
+       
+    /* Third Exercise */
+    
+    public static int countLegs(int cows) {
+        if (cows == 0) {
+            return 0;
+        } else {
+            return 4 + countLegs(cows - 1);
+        }
+    }
+
+    /* First Exercise */
+    
+    static int[][] inputMatrix = new int[][]{
+        {2, 2},
+        {4, 4},
+        {6, 5}};
+
+    public static double[] calcAbsRowVector(int[][] aMatrix) {
+
+        double[] result = new double[aMatrix.length];
+        double temp = 0.0;
+
+        for (int i = 0; i < aMatrix.length; i++) {
+            for (int j = 0; j < aMatrix[i].length; j++) {
+                temp = temp + Math.pow(aMatrix[i][j], 2);
+                //System.out.println(" I = " + i + " J = " + j + " Temp = " + temp);
+            }
+            result[i] = Math.sqrt(temp);
+            temp = 0.0;
+            //System.out.println(" Result at I " + i + " Result " + result[i]);
+        }
+
+        return result;
+    }
+
+    /* Second Exercise */
+    
+    static int[] input1 = new int[]{2, 7, 5, 34};
+    static int[] input2 = new int[]{3, 48, 4, 72};
+    
+    public static int[] mergeAndSortArrays(int[] firstArray, int[] secondArray) {
+
+        int[] resultArray = new int[firstArray.length * 2];
+        /* OK, both Arrays are the same size */
+
+        int offset = firstArray.length;
+
+        for (int i = 0; i < firstArray.length; i++) {
+            resultArray[i] = firstArray[i];
+        }
+        for (int i = 0; i < secondArray.length; i++) {
+            resultArray[i + offset] = secondArray[i];
+        }
+        
+        
+        
+        
+        /* Just for debugging */
+        System.out.println("Result Array " + Arrays.toString(resultArray));
+        
+        /*
+         * Die haeufigste Antwort wird die Verwendung der build - in Funktion 
+         * von Java zum Sortieren von Arrays sein
+        */
+        
+        Arrays.sort(resultArray);
+        
+         /*
+         * Dann nachfragen und den Bewerber das Array manuell mit einem 
+         * Algorithmus seiner Wahl (z.B. Quicksort oder einfache Maximumssuche)
+         * sortieren lassen
+        */
+        
+        /* Just for debugging */
+        System.out.println("Sorted Result Array " + Arrays.toString(resultArray));
+        
+        return resultArray;
+    }
+}