LeetCode 솔루션 분류
[11/1] 1706. Where Will the Ball Fall
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Medium
1986131Add to ListShareYou 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.lengthn == grid[i].length1 <= m, n <= 100grid[i][j]is1or-1.
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Submissions
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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.
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
