Data commit

Task/Move-to-front-algorithm/Python/move-to-front-algorithm-1.py

@@ -0,0 +1,28 @@
+from __future__ import print_function
+from string import ascii_lowercase
+
+SYMBOLTABLE = list(ascii_lowercase)
+
+def move2front_encode(strng, symboltable):
+    sequence, pad = [], symboltable[::]
+    for char in strng:
+        indx = pad.index(char)
+        sequence.append(indx)
+        pad = [pad.pop(indx)] + pad
+    return sequence
+
+def move2front_decode(sequence, symboltable):
+    chars, pad = [], symboltable[::]
+    for indx in sequence:
+        char = pad[indx]
+        chars.append(char)
+        pad = [pad.pop(indx)] + pad
+    return ''.join(chars)
+
+if __name__ == '__main__':
+    for s in ['broood', 'bananaaa', 'hiphophiphop']:
+        encode = move2front_encode(s, SYMBOLTABLE)
+        print('%14r encodes to %r' % (s, encode), end=', ')
+        decode = move2front_decode(encode, SYMBOLTABLE)
+        print('which decodes back to %r' % decode)
+        assert s == decode, 'Whoops!'

Task/Move-to-front-algorithm/Python/move-to-front-algorithm-2.py

@@ -0,0 +1,13 @@
+def m2f_e(s, st):
+    return [[st.index(ch), st.insert(0, st.pop(st.index(ch)))][0] for ch in s]
+
+def m2f_d(sq, st):
+    return ''.join([st[i], st.insert(0, st.pop(i))][0] for i in sq)
+
+ST = list('abcdefghijklmnopqrstuvwxyz')
+for s in ['broood', 'bananaaa', 'hiphophiphop']:
+    encode = m2f_e(s, ST[::])
+    print('%14r encodes to %r' % (s, encode), end=', ')
+    decode = m2f_d(encode, ST[::])
+    print('decodes back to %r' % decode)
+    assert s == decode, 'Whoops!'