Package g1701_1800.s1706_where_will_the_ball_fall

Class Solution

  • public class Solution
extends Object
    1706 - Where Will the Ball Fall.

    Medium

    You have a 2-D grid of size m x n representing a box, and you have n balls. The box is open on the top and bottom sides.

    Each cell in the box has a diagonal board spanning two corners of the cell that can redirect a ball to the right or to the left.

    • A board that redirects the ball to the right spans the top-left corner to the bottom-right corner and is represented in the grid as 1.
    • A board that redirects the ball to the left spans the top-right corner to the bottom-left corner and is represented in the grid as -1.

    We drop one ball at the top of each column of the box. Each ball can get stuck in the box or fall out of the bottom. A ball gets stuck if it hits a “V” shaped pattern between two boards or if a board redirects the ball into either wall of the box.

    Return an array answer of size n where answer[i] is the column that the ball falls out of at the bottom after dropping the ball from the ith column at the top, or -1 if the ball gets stuck in the box.

    Example 1:

    Input: grid = [[1,1,1,-1,-1],[1,1,1,-1,-1],[-1,-1,-1,1,1],[1,1,1,1,-1],[-1,-1,-1,-1,-1]]

    Output: [1,-1,-1,-1,-1]

    Explanation: This example is shown in the photo.

    Ball b0 is dropped at column 0 and falls out of the box at column 1.

    Ball b1 is dropped at column 1 and will get stuck in the box between column 2 and 3 and row 1.

    Ball b2 is dropped at column 2 and will get stuck on the box between column 2 and 3 and row 0.

    Ball b3 is dropped at column 3 and will get stuck on the box between column 2 and 3 and row 0.

    Ball b4 is dropped at column 4 and will get stuck on the box between column 2 and 3 and row 1.

    Example 2:

    Input: grid = [[-1]]

    Output: [-1]

    Explanation: The ball gets stuck against the left wall.

    Example 3:

    Input: grid = [[1,1,1,1,1,1],[-1,-1,-1,-1,-1,-1],[1,1,1,1,1,1],[-1,-1,-1,-1,-1,-1]]

    Output: [0,1,2,3,4,-1]

    Constraints:

    • m == grid.length
    • n == grid[i].length
    • 1 <= m, n <= 100
    • grid[i][j] is 1 or -1.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • findBall

        public int[] findBall​(int[][] grid)