- Added APL solutions by Richard Park.

5 files changed, 56 insertions, 0 deletions

diff --git a/challenge-055/richard-park/apl/FlipBinary.aplf b/challenge-055/richard-park/apl/FlipBinary.aplf
new file mode 100644
index 0000000000..248a6f09dc
--- /dev/null
+++ b/challenge-055/richard-park/apl/FlipBinary.aplf
@@ -0,0 +1,12 @@
+ FlipBinary←{
+⍝ ⍵: Binary number b of length n
+     n←≢b←⍵
+⍝ Flip 2 indices L≤R<N and count the number of 1s
+⍝ ←: L R pairs which result in maximum 1s
+     To←{⍺+⍳1+⍵-⍺}         ⍝ Integers ⍺ to ⍵ inclusive
+     flip←{⍵/⍨≤/¨⍵},⍳n n   ⍝ Possible flip indices L R
+     flerp←(⊃To/)¨flip     ⍝ Interpolate integers from L to R
+     f←⍵∘{~@⍵⊢⍺}¨flerp     ⍝ b flipped at each set of flip indices
+     max←⌈/sum←+/¨f        ⍝ Maximum number of 1s
+     flip[⍸sum=max]        ⍝ Flip indices which result in maximum 1s
+ }
diff --git a/challenge-055/richard-park/apl/Pmat.aplf b/challenge-055/richard-park/apl/Pmat.aplf
new file mode 100644
index 0000000000..12be0666b9
--- /dev/null
+++ b/challenge-055/richard-park/apl/Pmat.aplf
@@ -0,0 +1,6 @@
+ Pmat←{⎕ML←1             ⍝ dfns pmat: Permutation matrix of ⍳⍵.
+     {                   ⍝ perms of ⍳⍵:
+         1≥⍴⍵:↑,↓⍵       ⍝ short vector: done.
+         ↑⍪/⍵,∘∇¨⍵∘~¨⍵   ⍝ items prefix sub-perms of remainder.
+     }⍳⍵                 ⍝ permutations of identity perm.
+ }
diff --git a/challenge-055/richard-park/apl/WaveArray.aplf b/challenge-055/richard-park/apl/WaveArray.aplf
new file mode 100644
index 0000000000..06fdfa0dd9
--- /dev/null
+++ b/challenge-055/richard-park/apl/WaveArray.aplf
@@ -0,0 +1,13 @@
+ WaveArray←{
+⍝ Thanks to Total Array Ordering, an array ⍵ can be reordered so that its major cells, m, have the property
+⍝ (1⌷⍵)≥(2⌷⍵)≤(3⌷⍵)≥(4⌷⍵)≤...
+⍝ ⍵: Array
+⍝ ←: Array of rank (1+≢⍴⍵) where each major cell is a wave permutation of ⍵
+     n←≢⍵
+     p←⍵⌷⍤0 99⍨Pmat n        ⍝ Permutations of ⍵
+     gte←(¯1+n)⍴1 0          ⍝ Wave-array greater-than or equal pattern
+     lte←~gte                ⍝ Wave-array less-than or equal pattern
+     g←gte≡⍤1⊢2≥/(⍋⍋)⍤¯1⊢p   ⍝ Permutations with wave gte pattern
+     l←lte≡⍤1⊢2≤/(⍋⍋)⍤¯1⊢p   ⍝ Permutations with wave lte pattern
+     ∪(g∧l)⌿p                ⍝ Unique wave permutations of ⍵
+ }
diff --git a/challenge-055/richard-park/apl/ch-1.apl b/challenge-055/richard-park/apl/ch-1.apl
new file mode 100644
index 0000000000..248a6f09dc
--- /dev/null
+++ b/challenge-055/richard-park/apl/ch-1.apl
@@ -0,0 +1,12 @@
+ FlipBinary←{
+⍝ ⍵: Binary number b of length n
+     n←≢b←⍵
+⍝ Flip 2 indices L≤R<N and count the number of 1s
+⍝ ←: L R pairs which result in maximum 1s
+     To←{⍺+⍳1+⍵-⍺}         ⍝ Integers ⍺ to ⍵ inclusive
+     flip←{⍵/⍨≤/¨⍵},⍳n n   ⍝ Possible flip indices L R
+     flerp←(⊃To/)¨flip     ⍝ Interpolate integers from L to R
+     f←⍵∘{~@⍵⊢⍺}¨flerp     ⍝ b flipped at each set of flip indices
+     max←⌈/sum←+/¨f        ⍝ Maximum number of 1s
+     flip[⍸sum=max]        ⍝ Flip indices which result in maximum 1s
+ }
diff --git a/challenge-055/richard-park/apl/ch-2.apl b/challenge-055/richard-park/apl/ch-2.apl
new file mode 100644
index 0000000000..06fdfa0dd9
--- /dev/null
+++ b/challenge-055/richard-park/apl/ch-2.apl
@@ -0,0 +1,13 @@
+ WaveArray←{
+⍝ Thanks to Total Array Ordering, an array ⍵ can be reordered so that its major cells, m, have the property
+⍝ (1⌷⍵)≥(2⌷⍵)≤(3⌷⍵)≥(4⌷⍵)≤...
+⍝ ⍵: Array
+⍝ ←: Array of rank (1+≢⍴⍵) where each major cell is a wave permutation of ⍵
+     n←≢⍵
+     p←⍵⌷⍤0 99⍨Pmat n        ⍝ Permutations of ⍵
+     gte←(¯1+n)⍴1 0          ⍝ Wave-array greater-than or equal pattern
+     lte←~gte                ⍝ Wave-array less-than or equal pattern
+     g←gte≡⍤1⊢2≥/(⍋⍋)⍤¯1⊢p   ⍝ Permutations with wave gte pattern
+     l←lte≡⍤1⊢2≤/(⍋⍋)⍤¯1⊢p   ⍝ Permutations with wave lte pattern
+     ∪(g∧l)⌿p                ⍝ Unique wave permutations of ⍵
+ }