Data commit

Task/Huffman-coding/D/huffman-coding.d

@@ -0,0 +1,21 @@
+import std.stdio, std.algorithm, std.typecons, std.container, std.array;
+
+auto encode(alias eq, R)(Group!(eq, R) sf) /*pure nothrow @safe*/ {
+    auto heap = sf.map!(s => tuple(s[1], [tuple(s[0], "")]))
+                .array.heapify!q{b < a};
+
+    while (heap.length > 1) {
+        auto lo = heap.front; heap.removeFront;
+        auto hi = heap.front; heap.removeFront;
+        lo[1].each!((ref pair) => pair[1] = '0' ~ pair[1]);
+        hi[1].each!((ref pair) => pair[1] = '1' ~ pair[1]);
+        heap.insert(tuple(lo[0] + hi[0], lo[1] ~ hi[1]));
+    }
+    return heap.front[1].schwartzSort!q{ tuple(a[1].length, a[0]) };
+}
+
+void main() /*@safe*/ {
+    immutable s = "this is an example for huffman encoding"d;
+    foreach (const p; s.dup.sort().group.encode)
+        writefln("'%s'  %s", p[]);
+}