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[11/1] 1706. Where Will the Ball Fall

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작성일 2022.11.01 08:09

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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.

Accepted

81,172

Submissions

116,086

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링크

https://leetcode.com/problems/where-will-the-ball-fall/ 749 회 연결

익명
작성일 2022.11.01 08:09

Runtime: 245 ms, faster than 82.17% of Python3 online submissions for Where Will the Ball Fall.
Memory Usage: 14.4 MB, less than 30.84% of Python3 online submissions for Where Will the Ball Fall.

class Solution:
    def findBall(self, grid: List[List[int]]) -> List[int]:
        direction = {
            1:(1,1),-1:(1,-1)
        }
        
        ROW, COL = len(grid), len(grid[0])
        
        res = []
        
        for ball_col in range(COL):
            ball_c = ball_col
            ball_r = 0
            
            while ball_r < ROW:
                grid_dir = direction[grid[ball_r][ball_c]]
                
                side_grid_col = ball_c + grid_dir[1]
                # out of wall
                if side_grid_col < 0 or side_grid_col == COL: break
                # V shape
                if grid[ball_r][side_grid_col] == -grid_dir[1]: break
                
                ball_r += 1
                ball_c += grid_dir[1]
            
            if ball_r == ROW: res.append(ball_c)
            else: res.append(-1)
        
        return res

Runtime: 245 ms, faster than 82.17% of Python3 online submissions for Where Will the Ball Fall.
Memory Usage: 14.4 MB, less than 30.84% of Python3 online submissions for Where Will the Ball Fall.
[code=Python 3]class Solution:
    def findBall(self, grid: List[List[int]]) -> List[int]:
        direction = {
            1:(1,1),-1:(1,-1)
        }
        
        ROW, COL = len(grid), len(grid[0])
        
        res = []
        
        for ball_col in range(COL):
            ball_c = ball_col
            ball_r = 0
            
            while ball_r < ROW:
                grid_dir = direction[grid[ball_r][ball_c]]
                
                side_grid_col = ball_c + grid_dir[1]
                # out of wall
                if side_grid_col < 0 or side_grid_col == COL: break
                # V shape
                if grid[ball_r][side_grid_col] == -grid_dir[1]: break
                
                ball_r += 1
                ball_c += grid_dir[1]
            
            if ball_r == ROW: res.append(ball_c)
            else: res.append(-1)
        
        return res
                    
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