Initial data commit

Task/Huffman-coding/FreeBASIC/huffman-coding.basic

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+type block
+    freq as uinteger
+    chars as string
+end type
+
+type code
+    char as string*1
+    code as string
+end type
+
+sub bubble( lst() as block, n_l as uinteger )
+    for j as integer = n_l-1 to 0 step -1
+        if j>0 andalso lst(j).freq > lst(j-1).freq then
+            swap lst(j), lst(j-1)
+        endif
+    next j
+end sub
+
+dim as string Sample = "this is an example for huffman encoding"
+redim as block hufflist(0)
+hufflist(0).freq = 1 : hufflist(0).chars = mid(Sample,1,1)
+dim as boolean newchar
+dim as string*1 currchar
+dim as uinteger n_h = 1, n_c
+
+'read characters in one-by-one and simultaneously bubblesort them
+for i as uinteger = 2 to len(Sample)
+    currchar = mid(Sample,i,1)
+    newchar = true
+    for j as uinteger = 0 to n_h-1
+        if mid(Sample,i,1) = hufflist(j).chars then
+            hufflist(j).freq += 1
+            newchar = false
+        end if
+        if j>0 andalso hufflist(j).freq > hufflist(j-1).freq then
+            swap hufflist(j), hufflist(j-1)
+        endif
+    next j
+    if newchar then
+        redim preserve hufflist(0 to n_h)
+        hufflist(n_h).chars = currchar
+        hufflist(n_h).freq  = 1
+        n_h+=1
+    end if
+next i
+'one final pass of bubblesort may be necessary
+bubble hufflist(), n_h
+
+'initialise huffman code
+redim as code codelist(0 to n_h-1)
+for i as uinteger = 0 to n_h-1
+    codelist(i).char = hufflist(i).chars
+    codelist(i).code = ""
+next i
+n_c = n_h
+
+do
+    'characters in the least common block get "0" appended
+    for i as uinteger = 1 to len(hufflist(n_h-1).chars)
+        for j as uinteger = 0 to n_c-1
+            if codelist(j).char = mid(hufflist(n_h-1).chars,i,1) then
+                codelist(j).code = "0" + codelist(j).code
+            end if
+        next j
+    next i
+    'characters in the second-least common block get "1" appended
+    for i as uinteger = 1 to len(hufflist(n_h-2).chars)
+        for j as uinteger = 0 to n_c-1
+            if codelist(j).char = mid(hufflist(n_h-2).chars,i,1) then
+                codelist(j).code = "1" + codelist(j).code
+            end if
+        next j
+    next i
+    'combine the two least frequent blocks
+    hufflist(n_h-2).chars = hufflist(n_h-2).chars + hufflist(n_h-1).chars
+    hufflist(n_h-2).freq = hufflist(n_h-2).freq + hufflist(n_h-1).freq
+    redim preserve hufflist(0 to n_h-2)
+    n_h -= 1
+    'move the new combined block to its proper place in the list
+    bubble hufflist(), n_h
+loop until n_h = 1
+
+for i as uinteger = 0 to n_c - 1
+    print "'"+codelist(i).char+"'", codelist(i).code
+next i