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114 lines
2.9 KiB
Markdown
114 lines
2.9 KiB
Markdown
---
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id: 69162d64f96574d9bb629efc
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title: "Challenge 111: Ball Trajectory"
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challengeType: 29
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dashedName: challenge-111
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---
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# --description--
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Today's challenge is inspired by the video game Pong, which was released November 29, 1972.
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Given a matrix (array of arrays) that includes the location of the ball (`2`), and the previous location of the ball (`1`), return the matrix indices for the next location of the ball.
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- The ball always moves in a straight line.
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- The movement direction is determined by how the ball moved from `1` to `2`.
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- The edges of the matrix are considered walls. If the ball hits a:
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- top or bottom wall, it bounces by reversing its vertical direction.
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- left or right wall, it bounces by reversing its horizontal direction.
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- corner, it bounces by reversing both directions.
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# --hints--
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`get_next_location([[0,0,0,0], [0,0,0,0], [0,1,2,0], [0,0,0,0]])` should return `[2, 3]`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(get_next_location([[0,0,0,0], [0,0,0,0], [0,1,2,0], [0,0,0,0]]), [2, 3])`)
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}})
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```
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`get_next_location([[0,0,0,0], [0,0,1,0], [0,2,0,0], [0,0,0,0]])` should return `[3, 0]`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(get_next_location([[0,0,0,0], [0,0,1,0], [0,2,0,0], [0,0,0,0]]), [3, 0])`)
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}})
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```
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`get_next_location([[0,2,0,0], [1,0,0,0], [0,0,0,0], [0,0,0,0]])` should return `[1, 2]`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(get_next_location([[0,2,0,0], [1,0,0,0], [0,0,0,0], [0,0,0,0]]), [1, 2])`)
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}})
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```
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`get_next_location([[0,0,0,0], [0,0,0,0], [2,0,0,0], [0,1,0,0]])` should return `[1, 1]`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(get_next_location([[0,0,0,0], [0,0,0,0], [2,0,0,0], [0,1,0,0]]), [1, 1])`)
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}})
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```
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`get_next_location([[0,0,0,0], [0,0,0,0], [0,0,1,0], [0,0,0,2]])` should return `[2, 2]`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(get_next_location([[0,0,0,0], [0,0,0,0], [0,0,1,0], [0,0,0,2]]), [2, 2])`)
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}})
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```
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# --seed--
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## --seed-contents--
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```py
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def get_next_location(matrix):
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return matrix
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```
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# --solutions--
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```py
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def get_next_location(matrix):
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prev = None
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curr = None
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for r in range(len(matrix)):
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for c in range(len(matrix[0])):
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if matrix[r][c] == 1:
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prev = (r, c)
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if matrix[r][c] == 2:
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curr = (r, c)
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prev_row, prev_col = prev
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curr_row, curr_col = curr
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dir_x = curr_col - prev_col
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dir_y = curr_row - prev_row
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next_row = curr_row + dir_y
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next_col = curr_col + dir_x
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max_row = len(matrix) - 1
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max_col = len(matrix[0]) - 1
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if next_col < 0 or next_col > max_col:
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dir_x *= -1
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if next_row < 0 or next_row > max_row:
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dir_y *= -1
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next_row = curr_row + dir_y
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next_col = curr_col + dir_x
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return [next_row, next_col]
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```
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