Merge pull request JuliaLang#115 from CNOT/master

added spiral-matrix

config.json

@@ -407,6 +407,18 @@
         "exceptions"
       ]
     },
+    {
+    "uuid": "3a2facfd-5ec8-49a0-a5aa-2229f07da896",
+    "slug": "spiral-matrix",
+    "core": false,
+    "unlocked_by": null,
+    "difficulty": 3,
+    "topics": [
+    "matrix",
+    "mathematics",
+    "iterators"
+    ]
+    },
     {
       "slug": "isbn-verifier",
       "uuid": "22b64a2b-7f08-444d-be6e-8b42e5c9207c",

exercises/spiral-matrix/README.md

@@ -0,0 +1,31 @@
+# Spiral Matrix
+
+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
+
+```text
+1 2 3
+8 9 4
+7 6 5
+```
+
+###### Spiral matrix of size 4
+
+```text
+ 1  2  3 4
+12 13 14 5
+11 16 15 6
+10  9  8 7
+```
+## Source
+
+Reddit r/dailyprogrammer challenge #320 [Easy] Spiral Ascension. [https://www.reddit.com/r/dailyprogrammer/comments/6i60lr/20170619_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.

exercises/spiral-matrix/example.jl

@@ -0,0 +1,9 @@
+#Credit to u/SingularInfinity on Redit: https://www.reddit.com/r/dailyprogrammer/comments/6i60lr/20170619_challenge_320_easy_spiral_ascension/djb8po0
+
+function spiral_matrix(n::Int)
+    n < 0 && throw(DomainError("n should be positive"))
+    n == 0 && return Matrix{Int}(0,0)
+    n == 1 && return reshape(Int[1], 1, 1)
+    m = (2n - 1) .+ spiral_matrix(n-1)
+    return [ RowVector(1:n); rot180(m) n+1:2n-1 ]
+end

exercises/spiral-matrix/runtests.jl

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+using Base.Test
+
+include("spiral-matrix.jl")
+
+
+@testset "Different valid values" begin
+    @testset "Empty spiral" begin
+        @test spiral_matrix(0) == Matrix{Int}(0,0)
+    end
+    @testset "Trivial spiral" begin
+        @test spiral_matrix(1) == reshape([1],(1,1))
+    end
+    @testset "Spiral of size 2" begin
+        @test spiral_matrix(2) == [1 2; 4 3]
+    end
+    @testset "Spiral of size 3" begin
+        @test spiral_matrix(3) == [1 2 3; 8 9 4; 7 6 5]
+    end
+    @testset "Spiral of size 4" begin
+        @test spiral_matrix(4) == [1 2 3 4; 12 13 14 5; 11 16 15 6; 10 9 8 7]
+    end
+    @testset "Spiral of size 5" begin
+        @test spiral_matrix(5) == [1 2 3 4 5; 16 17 18 19 6; 15 24 25 20 7; 14 23 22 21 8; 13 12 11 10 9]
+    end
+end

exercises/spiral-matrix/spiral-matrix.jl

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+function spiral_matrix(n::Int)
+
+end