CSC212 Homework 2 Solutions 2014

--D. Thiebaut (talk) 07:38, 28 September 2014 (EDT)

---

Problem #1

PythonList.java

// put your PythonList.java file here
public class PythonList {
    public int[] array = null;
    private int maxdim;
    private int end = 0;
    
    PythonList(int m) {
        maxdim = m;
        end = 0;
        array = new int[maxdim];
    }
    
    PythonList() {
        this(100);
    }

    private boolean isValid( int i ) {
        return ( i >= 0 && i < end );
    }

    public void setAt( int i, int n ) {
        if ( ! isValid( i ) ) 
            return;
        array[i] = n;
    }

    public int index( int n ) {
        for ( int i=0; i < end; i++ ) {
            //if ( array[i]==n )
            if ( at(i) == n )
                return i;
        }
        return -1;
    }

    public int rindex( int n ) {
        for ( int i=end-1; i >= 0; i-- )
            if ( array[i]==n )
                return i;
        
        return -1;
    }

   
    public void append(int n) {
        if (end <= array.length - 1) {
            array[end++] = n;
            return;
        }
        int[] temp = new int[maxdim * 2];
        for (int i = 0; i < array.length; i++)
            temp[i] = array[i];
        array = temp;
        array[end++] = n;
        maxdim = maxdim * 2;
    }
    
    public int length() {
        return end;
    }
    
    public int at(int index) {
        
        if (index >= 0 && index < array.length)
            return array[index];
        // this is bad... we'll fix it later...
        else
            return -1;
    }
    
    public static void main(String[] args) {
        // --- Test List ---
        PythonList L = new PythonList(5);
        
        for (int i = 0; i < 11; i++)
            L.append(i*2);
        
        L.append( 2 );

        for (int i = 0; i < L.length(); i++)
            System.out.println(L.at(i));


        System.out.println( " index("+ 2 +") = " + L.index(2) );
        System.out.println( " rindex("+ 2 +") = " + L.rindex(2) );


    }
}

PascalList.java

// Put your PascalList.java file here

public class PascalList {
    static private final int ROW = 9;

    public PascalList() {
        
    }

    static public void main( String[] args ) {
        PythonList row = new PythonList( 3 );
        row.append( 1 );
        for ( int i=1; i<ROW; i++ ) 
            row.append( 0 );
        
        //row.array[0] = 1;
        
        for ( int i=1; i<ROW; i++ ) {
            for ( int k=ROW-1; k>0; k-- )
                row.setAt(k,  row.at(k-1) + row.at(k) );
        }
        for ( int i=0; i<row.length(); i++ ) 
            System.out.println( row.at(i) + " " );
        System.out.println();
    }
}

Problem #2

PythonList2.java

// place your code here...
public class PythonList2 {
    private String[] array = null;
    private int maxdim;
    private int end = 0;
    
    PythonList2(int m) {
        maxdim = m;
        end = 0;
        array = new String[maxdim];
    }
    
    PythonList2() {
        this(100);
    }

    private boolean isValid( int i ) {
        return ( i >= 0 && i < end );
    }

    public void setAt( int i, String n ) {
        if ( ! isValid( i ) ) 
            return;
        array[i] = n;
    }

    public int index( String n ) {
        for ( int i=0; i < end; i++ ) {
            if ( at(i) == n )
                return i;
        }
        return -1;
    }

    public int rindex( String n ) {
        for ( int i=end-1; i >= 0; i-- )
            if ( array[i]==n )
                return i;
        
        return -1;
    }

   
    public void append(String  n) {
        if (end <= array.length - 1) {
            array[end++] = n;
            return;
        }
        String[] temp = new String[maxdim * 2];
        for (int i = 0; i < array.length; i++)
            temp[i] = array[i];
        array = temp;
        array[end++] = n;
        maxdim = maxdim * 2;
    }
    
    public int length() {
        return end;
    }
    
    public String at(int index) {
        
        if (index >= 0 && index < array.length)
            return array[index];
        else
            return null;
    }
    
    public static void main(String[] args) {
        // --- Test List ---
        PythonList2 dwarves = new PythonList2(5);

        dwarves.append("Blick2");
        dwarves.append("Flick2");
        dwarves.append("Glick2");
        dwarves.append("Plick2");
        dwarves.append("Quee2");
        dwarves.append("Snick2");
        dwarves.append("Whick2");

        System.out.println("Snow White's friends:");
        for (int i = 0; i < dwarves.length(); i++)
            System.out.println(dwarves.at(i));

        String dwarf;
        dwarf = dwarves.at(-1);
        if (dwarf != null)
            System.out.println(dwarf);
        dwarf = dwarves.at(20);
        if (dwarf != null)
            System.out.println(dwarf);

        int n = dwarves.index( "Quee" );
        if ( n != -1 ) 
            System.out.println( "Quee found at Index: " + n );
        else
            System.out.println( "Quee not found" );

        n = dwarves.rindex( "Quee" );
        if ( n != -1 ) 
            System.out.println( "Quee found at Index: " + n );
        else
            System.out.println( "Quee not found" );

        n = dwarves.index( "Queen" );
        if ( n != -1 ) 
            System.out.println( "Queen found at Index: " + n );
        else
            System.out.println( "Queen not found" );

    }
}