challenge-065/richard-park/apl/ch-2.aplf


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 PalindromePartition←{
⍝ For character vector ⍵, print all possible partitions that give palindromes.
⍝ Return -1 if none found.
⍝ Partitions should not overlap. For example, for given string “abaab”, the partition “aba” and “baab” would not be valid, since they overlap.
     ⎕IO←1
     PPTest←((~' '∊⊢)∧(⌽≡⊢)∧(1<≢))¨   ⍝ No spaces, palindrome, more than 1 char
     len←≢⍵
     pvec←1,1↓⍤1⍉2⊥⍣¯1⊢¯1+⍳2*len      ⍝ All partition vectors of length len←≢⍵
     parts←pvec⊂⍤1⊢⍵                  ⍝ All partition candidates
     ispal←{⊂⍵/⍨PPTest ⍵}⍤1⊢parts     ⍝ Palindrome partition candidates
     ispp←{⍵⌿⍨∊0≠⍴¨⍵}∪ispal           ⍝ Remove empty partitions
     upp←{⍵⌿⍨1=+/⍵∘.(∧/∊)⍵}ispp       ⍝ Remove subset partitions
     0=⍴upp:¯1                        ⍝ No palindrome partitions
     upp
 }