Provided Code

public class Position
{
        public Position(int r, int c) {
        /* given */
    }
        public int getRow() {
        /* given */
    }
        public int getCol() {
        /* given */
    }
}

// Methods to implement are in a separate class (not shown):
public static Position findPosition(String str, String[][] grid)
{ /* to be implemented in part (a) */ }

public static ArrayList allPositions(String str, String[][] grid)
{ /* to be implemented in part (b) */ }

Part A — findPosition (5 Points)

Write findPosition(). Search the 2D array grid for str. Return a new Position(row, col) for the first match found (in row-major order), or null if str is not in grid.

Check Answer Clear

public static Position findPosition(String str, String[][] grid)
{
    for (int r = 0; r < grid.length; r++)
    {
        for (int c = 0; c < grid[r].length; c++)
        {
            if (grid[r][c].equals(str))
            {
                return new Position(r, c);
            }
        }
    }
    return null;
}

Part B — allPositions (4 Points)

Write allPositions(). Return an ArrayList containing a Position object for every location where str appears in grid. The list may be empty if str does not appear.

Check Answer Clear

public static ArrayList allPositions(String str, String[][] grid)
{
    ArrayList result = new ArrayList();

    for (int r = 0; r < grid.length; r++)
    {
        for (int c = 0; c < grid[r].length; c++)
        {
            if (grid[r][c].equals(str))
            {
                result.add(new Position(r, c));
            }
        }
    }
    return result;
}

Frequently Asked Questions