# 1706. Where Will the Ball Fall

https://leetcode.com/problems/where-will-the-ball-fall

## Description

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`.

## ac

```java
```
