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raymondchen625's solution

to Spiral Matrix in the Go Track

Published at Mar 27 2019 · 0 comments
Instructions
Test suite
Solution

Given the size, return a square matrix of numbers in spiral order.

The matrix should be filled with natural numbers, starting from 1 in the top-left corner, increasing in an inward, clockwise spiral order, like these examples:

Spiral matrix of size 3
1 2 3
8 9 4
7 6 5
Spiral matrix of size 4
 1  2  3 4
12 13 14 5
11 16 15 6
10  9  8 7

Running the tests

To run the tests run the command go test from within the exercise directory.

If the test suite contains benchmarks, you can run these with the --bench and --benchmem flags:

go test -v --bench . --benchmem

Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.

Further information

For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.

Source

Reddit r/dailyprogrammer challenge #320 [Easy] Spiral Ascension. https://www.reddit.com/r/dailyprogrammer/comments/6i60lr/20170619_challenge_320_easy_spiral_ascension/

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

spiral_matrix_test.go

package spiralmatrix

import (
	"reflect"
	"testing"
)

var testCases = []struct {
	description string
	input       int
	expected    [][]int
}{
	{
		description: "empty spiral",
		input:       0,
		expected:    [][]int{},
	},
	{
		description: "trivial spiral",
		input:       1,
		expected: [][]int{
			{1},
		},
	},
	{
		description: "spiral of size 2",
		input:       2,
		expected: [][]int{
			{1, 2},
			{4, 3},
		},
	},
	{
		description: "spiral of size 3",
		input:       3,
		expected: [][]int{
			{1, 2, 3},
			{8, 9, 4},
			{7, 6, 5},
		},
	},
	{
		description: "spiral of size 4",
		input:       4,
		expected: [][]int{
			{1, 2, 3, 4},
			{12, 13, 14, 5},
			{11, 16, 15, 6},
			{10, 9, 8, 7},
		},
	},
}

func TestSpiralMatrix(t *testing.T) {
	for _, testCase := range testCases {
		matrix := SpiralMatrix(testCase.input)
		if !reflect.DeepEqual(matrix, testCase.expected) {
			t.Fatalf("FAIL: %s\n\tSpiralMatrix(%v)\nexpected: %v\ngot     : %v",
				testCase.description, testCase.input, testCase.expected, matrix)
		}
		t.Logf("PASS: %s", testCase.description)
	}
}

func BenchmarkSpiralMatrix(b *testing.B) {
	for i := 0; i < b.N; i++ {
		for _, testCase := range testCases {
			SpiralMatrix(testCase.input)
		}
	}
}
package spiralmatrix

// SpiralMatrix constructs a square matrix of numbers in spiral order.
// Parameter d is the dimension number
func SpiralMatrix(d int) [][]int {
	matrix := make([][]int, d)
	for i := range matrix {
		matrix[i] = make([]int, d)
	}
	// Record the moving direction and turn clockwise if edge or filled item is reached
	row, col := 0, 0
	right := true
	left, up, down := false, false, false
	for i := 1; i <= d*d; i++ {
		matrix[row][col] = i
		if right {
			if col+1 < d && matrix[row][col+1] == 0 {
				col++
			} else {
				right, left, up = false, false, false
				down = true
				row++
			}
		} else if left {
			if col-1 >= 0 && matrix[row][col-1] == 0 {
				col--
			} else {
				up = true
				left, right, down = false, false, false
				row--
			}
		} else if up {
			if row-1 >= 0 && matrix[row-1][col] == 0 {
				row--
			} else {
				right = true
				left, up, down = false, false, false
				col++
			}
		} else if down {
			if row+1 < d && matrix[row+1][col] == 0 {
				row++
			} else {
				left = true
				right, up, down = false, false, false
				col--
			}
		}
	}
	return matrix
}

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