A-M baby

Task/Huffman-coding/Go/huffman-coding-2.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+    "container/heap"
+    "fmt"
+)
+
+type coded struct {
+    sym  rune
+    code string
+}
+
+type counted struct {
+    total int
+    syms []coded
+}
+
+type cHeap []counted
+
+// satisfy heap.Interface
+func (c cHeap) Len() int           { return len(c) }
+func (c cHeap) Less(i, j int) bool { return c[i].total < c[j].total }
+func (c cHeap) Swap(i, j int)      { c[i], c[j] = c[j], c[i] }
+func (c *cHeap) Push(ele interface{}) {
+    *c = append(*c, ele.(counted))
+}
+func (c *cHeap) Pop() (popped interface{}) {
+    popped = (*c)[len(*c)-1]
+    *c = (*c)[:len(*c)-1]
+    return
+}
+
+func encode(sym2freq map[rune]int) []coded {
+    var ch cHeap
+    for sym, freq := range sym2freq {
+        ch = append(ch, counted{freq, []coded{{sym: sym}}})
+    }
+    heap.Init(&ch)
+    for len(ch) > 1 {
+        a := heap.Pop(&ch).(counted)
+        b := heap.Pop(&ch).(counted)
+        for i, c := range a.syms {
+            a.syms[i].code = "0" + c.code
+        }
+        for i, c := range b.syms {
+            b.syms[i].code = "1" + c.code
+        }
+        heap.Push(&ch, counted{a.total + b.total, append(a.syms, b.syms...)})
+    }
+    return heap.Pop(&ch).(counted).syms
+}
+
+const txt = "this is an example for huffman encoding"
+
+func main() {
+    sym2freq := make(map[rune]int)
+    for _, c := range txt {
+        sym2freq[c]++
+    }
+    table := encode(sym2freq)
+    fmt.Println("Symbol  Weight Huffman Code")
+    for _, c := range table {
+        fmt.Printf("     %c    %d    %s\n", c.sym, sym2freq[c.sym], c.code)
+    }
+}