In this approach, I used a dictionary ball_colors to keep track of the latest color assigned to each ball. Also, I added a set called distinct_colors to store all unique colors in use.
For each query [x, y], I first check if ball x has already been assigned a color. If it has and the color is different from y, I decrement the count of the old color in a dictionary color_count. If the count reaches zero, I remove the old color from distinct_colors. Then, I update ball x with the new color y and update its count in color_count. Finally, I add y to distinct_colors and append the size of distinct_colors to my result list.
