freecodecamp--freecodecamp/curriculum/challenges/english/blocks/daily-coding-challenges-python/69b5b2be76ec8135a7fbe974.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
69b5b2be76ec8135a7fbe974	Challenge 245: Spiral Matrix	29	challenge-245

--description--

Given a 2D matrix, return a flat array with all of its values in clockwise order.

The returned array should have the top-left value first, move right along the top row, then down the right column, then left along the bottom row, then up the left column. Repeat inward for any remaining layers.

For example, given:

[
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9]
]

Return [1, 2, 3, 6, 9, 8, 7, 4, 5].

--hints--

spiral_matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) should return [1, 2, 3, 6, 9, 8, 7, 4, 5].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(spiral_matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]), [1, 2, 3, 6, 9, 8, 7, 4, 5])`)
}})

spiral_matrix([["a", "b", "c", "d"], ["l", "m", "n", "e"], ["k", "p", "o", "f"], ["j", "i", "h", "g"]]) should return ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(spiral_matrix([["a", "b", "c", "d"], ["l", "m", "n", "e"], ["k", "p", "o", "f"], ["j", "i", "h", "g"]]), ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p"])`)
}})

spiral_matrix([[True, False, False], [False, True, True], [False, True, False], [True, True, False]]) should return [True, False, False, True, False, False, True, True, False, False, True, True].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(spiral_matrix([[True, False, False], [False, True, True], [False, True, False], [True, True, False]]), [True, False, False, True, False, False, True, True, False, False, True, True])`)
}})

spiral_matrix([[25, 24, 23, 22, 21], [10, 9, 8, 7, 20], [11, 2, 1, 6, 19], [12, 3, 4, 5, 18], [13, 14, 15, 16, 17]]) should return [25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(spiral_matrix([[25, 24, 23, 22, 21], [10, 9, 8, 7, 20], [11, 2, 1, 6, 19], [12, 3, 4, 5, 18], [13, 14, 15, 16, 17]]), [25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1])`)
}})

--seed--

--seed-contents--

def spiral_matrix(matrix):

    return matrix

--solutions--

def spiral_matrix(matrix):
    result = []
    top, bottom = 0, len(matrix) - 1
    left, right = 0, len(matrix[0]) - 1

    while top <= bottom and left <= right:
        for i in range(left, right + 1):
            result.append(matrix[top][i])
        top += 1

        for i in range(top, bottom + 1):
            result.append(matrix[i][right])
        right -= 1

        if top <= bottom:
            for i in range(right, left - 1, -1):
                result.append(matrix[bottom][i])
            bottom -= 1

        if left <= right:
            for i in range(bottom, top - 1, -1):
                result.append(matrix[i][left])
            left += 1

    return result