Data update

2026-04-30 12:34:36 -04:00 · 2026-04-30 12:34:36 -04:00 · cbaf4c4b64
commit cbaf4c4b64
parent 4bb20c9b71
12390 changed files with 318560 additions and 27248 deletions
--- a/Task/Move-to-front-algorithm/Fortran/move-to-front-algorithm.f
+++ b/Task/Move-to-front-algorithm/Fortran/move-to-front-algorithm.f
@ -0,0 +1,114 @@
+! Move-to-front algorithm
+! tested with Intel ifx (IFX) 2025.2.1 20250806             on Kubuntu 25.10
+!             GNU Fortran (Ubuntu 15.2.0-4ubuntu4) 15.2.0   on Kubuntu 25.10
+!             VSI Fortran x86-64 V8.7-001                   on OpenVMS x86_64 V9.2-3
+! No Non-standard features used, should compile on any fairly recent Fortran.
+! U.B., February 2026
+!=========================================================================================
+program FrontMove
+implicit none
+
+! Starting sequence in the local symbol tables in 2 subroutines
+character (len=26), parameter :: startSymbolTab = 'abcdefghijklmnopqrstuvwxyz'
+
+! The test cases of the task description:
+call EncodeAndCrossCheck ('broood')
+call EncodeAndCrossCheck ('bananaaa')
+call EncodeAndCrossCheck ('hiphophiphop')
+
+! Two more tests: What happens in MoveToFront() if char appears at the beginning ('a')
+! or at the end ('z') of the symbol table?
+call EncodeAndCrossCheck ('anton')
+call EncodeAndCrossCheck ('zwareshagz')
+
+contains
+
+! =========================================================================
+! Encode a given text string using the Move-to-fromt algorithm, then
+! decode the resultant sequence of numbers, to be compared to the original.
+! =========================================================================
+subroutine EncodeAndCrossCheck (text)
+
+character (len=*), intent(in) :: text         ! Input: the text to encode
+
+integer, dimension(len(text)) :: code         ! Resultant numeric array
+
+character (len=26) :: SymTab                  ! The symbol table to work with
+integer :: l                                  ! LEngth of input text
+integer :: ii, idx                            ! Loop index, Pos of a char inside Symbol Table
+
+! Initialize work table
+SymTab = startSymbolTab
+l  = len (text)
+
+write (*,'(A, T13, A)', advance='no')   text, ' ->'
+! Encoding Algorithm:
+!    for each symbol of the input sequence:
+!        output the index of the symbol in the symbol table
+!        move that symbol to the front of the symbol table
+
+do ii=1, l
+  idx = index (SymTab, text(ii:ii))
+  code (ii) = idx-1                           ! Code muss be null-based
+  write (*, '(I3)', advance='no')    code(ii)
+  call moveToFront (SymTab, idx)
+end do
+do ii=3*l,36
+  write (*,'(x)', advance='no')                              ! some space to format output
+enddo
+write (*,'(A)', advance='no')    ' -> '
+! Now decode the resultant code and hope to see again the original text.
+call decodeAndCheck (code, l, text)
+
+end subroutine EncodeAndCrossCheck
+
+
+! =====================================================================================
+! Decode a given array of numbers and check if the rtesult matches the given input text
+! =====================================================================================
+subroutine decodeAndCheck (code, l, text)
+
+integer , intent(in) ::l
+integer, dimension(l), intent(in) :: code
+character (len=*), intent(in) :: text         ! the text to compare to the decode result.
+
+character (len=26) :: SymTab
+integer :: ii, idx
+logical :: mismatch
+
+! # Using the same starting symbol table
+SymTab = startSymbolTab
+mismatch = .false.
+
+! Decoding Algorithm:
+!    for each index of the input sequence:
+!        output the symbol at that index of the symbol table
+!        move that symbol to the front of the symbol table
+do ii=1, l
+  idx = code(ii) + 1
+  write (*, '(A1)', advance='no')    SymTab (idx:idx)
+  if (SymTab (idx:idx) .ne. text (ii:ii)) mismatch = .true.
+  call moveToFront (SymTab, idx)
+end do
+
+if (.not. mismatch) then
+  write (*,*) '(Success)'
+else
+  write (*,*) 'ERROR.'
+endif
+
+end subroutine decodeAndCheck
+
+
+! =========================================================================
+! Move the character found at index 'ind' in the string "'txt' to the front
+! =========================================================================
+subroutine moveToFront (txt, ind)
+character (len=*), intent(inout) :: txt
+integer, intent(in) :: ind
+
+! Rearrange txt: character at ind, then everything in front of ind, then everything behind.
+txt = txt(ind:ind) // txt(:ind-1) // txt (ind+1:)
+end subroutine moveToFront
+
+end program FrontMove