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g1701_1800.s1706_where_will_the_ball_fall.readme.md Maven / Gradle / Ivy

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:**

**![](https://assets.leetcode.com/uploads/2019/09/26/ball.jpg)**

**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`.