4.31 The One-Lane Bridge. Cars coming from the north and the south arrive at a one- lane bridge. Cars heading in the same direction can cross the bridge at the same time, but cars heading in opposite directions cannot. (a) Develop a solution to this problem. First specify a global invariant, then develop a solution using semaphores for synchronization. Do not worry about fairness. (b) Modify your answer to (b) to ensure that any car that is waiting to cross the bridge eventually gets to do so. You may want to solve the problem differently. (Hint: Use the technique of passing the baton.)

Your objective is to write the solution to the 9 × 9 sudoku puzzle below. You must write in the digits 1 through 9 in each row such that no digit is repeated vertically, horizontally and in each box. In your solution, write each row on itsown line; and for each row, write each digit enclosed in square braces. For instance, if the row is (1, 2, 3, 4, 5, 6, 7, 8, 9), then you would type [1][2][3][4][5][6][7][8][9] for that row.

Your objective is to write the solution to the 9 × 9 sudoku puzzle below. You must write in the digits 1 through 9 in each row such that no digit is repeated vertically, horizontally and in each box. In your solution, write each row on itsown line; and for each row, write each digit enclosed in square braces. For instance, if the row is (1, 2, 3, 4, 5, 6, 7, 8, 9), then you would type [1][2][3][4][5][6][7][8][9] for that row.

Conway's Game of Life: This is a zero person game with the following rules: (see Wikipedia for example) Any live cell with fewer than two live neighbours dies, as if by underpopulation. Any live cell with two or three live neighbours lives on to the next generation. Any live cell with more than three live neighbours dies, as if by overpopulation. Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction. Remember the oscillator or blinker of 3 cells. You can also find this blinker on Wikipedia. 1 21 1 2 1 21 3. 4 6 4. 6. 4 8. 9 8 9 #1 #2. #3 5. Consider now these 3 creatures at stage 1: Show how they look like in the next two stages: stage 2 and stage 3. Explain how you get the answers Creature 1 Creature 2 Creature 3 (here creature 1 is the blinker of 3 cells, horizontally; creature 2 consists of two adjacent cells, creature 3 consists of 4 adjacent cells horiztonally) ww (d) Creature 1 (10%), (e) Creature 2 (8%), (f) Creature 3 (20%)