Data commit

Task/Huffman-coding/Python/huffman-coding-1.py

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+from heapq import heappush, heappop, heapify
+from collections import defaultdict
+
+def encode(symb2freq):
+    """Huffman encode the given dict mapping symbols to weights"""
+    heap = [[wt, [sym, ""]] for sym, wt in symb2freq.items()]
+    heapify(heap)
+    while len(heap) > 1:
+        lo = heappop(heap)
+        hi = heappop(heap)
+        for pair in lo[1:]:
+            pair[1] = '0' + pair[1]
+        for pair in hi[1:]:
+            pair[1] = '1' + pair[1]
+        heappush(heap, [lo[0] + hi[0]] + lo[1:] + hi[1:])
+    return sorted(heappop(heap)[1:], key=lambda p: (len(p[-1]), p))
+
+txt = "this is an example for huffman encoding"
+symb2freq = defaultdict(int)
+for ch in txt:
+    symb2freq[ch] += 1
+# in Python 3.1+:
+# symb2freq = collections.Counter(txt)
+huff = encode(symb2freq)
+print "Symbol\tWeight\tHuffman Code"
+for p in huff:
+    print "%s\t%s\t%s" % (p[0], symb2freq[p[0]], p[1])