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Provided Code

public class LightBoard
{
    private boolean[][] lights;
    /** Initializes lights: each light has 40% probability of being on.
     *  Precondition: numRows > 0, numCols > 0 */
        public LightBoard(int numRows, int numCols) {
        /* part (a) */
    }
    /** Evaluates light at row, col using 3 rules.
     *  Precondition: row and col are valid indexes */
        public boolean evaluateLight(int row, int col) {
        /* part (b) */
    }
}

Part A — 4 Points

Write the LightBoard constructor: initialize lights as a numRows × numCols boolean array where each light has a 40% probability of being set to true (on).

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public LightBoard(int numRows, int numCols)
{
    lights = new boolean[numRows][numCols];
    for (int r = 0; r < numRows; r++)
    {
        for (int c = 0; c < numCols; c++)
        {
            lights[r][c] = Math.random() < 0.4;
        }
    }
}

Part B — 5 Points

Write evaluateLight: count on-lights in column col (including the current light), then apply three rules to determine return value.

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public boolean evaluateLight(int row, int col)
{
    int onCount = 0;
    for (int r = 0; r < lights.length; r++)
    {
        if (lights[r][col])
        {
            onCount++;
        }
    }
    if (lights[row][col] && onCount % 2 == 0)
    {
        return false;
    }
    if (!lights[row][col] && onCount % 3 == 0)
    {
        return true;
    }
    return lights[row][col];
}

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