Provided Code

public class SparseArrayEntry
{
        public SparseArrayEntry(int r, int c, int v) {
        /* given */
    }
        public int getRow() {
        /* given */
    }
        public int getCol() {
        /* given */
    }
        public int getValue() {
        /* given */
    }
}

public class SparseArray
{
    private int numRows, numCols;
    private ArrayList entries;

        public int getValueAt(int row, int col) {
        /* part (a) */
    }
        public void removeColumn(int col) {
        /* part (b) */
    }
}

Part A — getValueAt (3 Points)

Write getValueAt(). Return the value of the entry at (row, col), or 0 if no entry exists at that position.

Check Answer Clear

public int getValueAt(int row, int col)
{
    for (SparseArrayEntry e : entries)
    {
        if (e.getRow() == row && e.getCol() == col)
        {
            return e.getValue();
        }
    }
    return 0;
}

Part B — removeColumn (6 Points)

Write removeColumn(). Remove all entries in column col. Then decrement the column value of all remaining entries that were in a column greater than col (since those columns shift left by one).

Check Answer Clear

public void removeColumn(int col)
{
    for (int i = entries.size() - 1; i >= 0; i--)
    {
        SparseArrayEntry e = entries.get(i);

        if (e.getCol() == col)
        {
            entries.remove(i);
        }
        else if (e.getCol() > col)
        {
            entries.set(i, new SparseArrayEntry(
                e.getRow(), e.getCol() - 1, e.getValue()));
        }
    }
    numCols--;
}

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