# wei's solution

## to Spiral Matrix in the Go Track

Published at Feb 21 2020 · 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
``````

## Coding the solution

Look for a stub file having the name spiral_matrix.go and place your solution code in that file.

## 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

var (
up    = 'u'
right = 'r'
down  = 'd'
left  = 'l'
)

func SpiralMatrix(n int) [][]int {

if n == 0 {
return [][]int{}
}

m := make([][]int, n)

for i := range m {
m[i] = make([]int, n)
}

i, j, k := 0, 0, 1
direction := right

for k <= n*n {
switch direction {
case right:
m[i][j] = k
if j == n-1 || m[i][j+1] != 0{
direction = down
i++
} else {
j++
}
case down:
m[i][j] = k
if i == n-1 || m[i+1][j] != 0{
direction = left
j--
} else {
i++
}
case left:
m[i][j] = k
if j == 0 || m[i][j-1] != 0 {
direction = up
i--
} else {
j--
}
case up:
m[i][j] = k
if i == 0 || m[i-1][j] != 0 {
direction = right
j++
} else {
i--
}
}

k++
}

return m
}``````