golang huffman

// Huffman Coding in Golangpackage mainimport (    "container/heap"    "fmt")type HuffmanTree interface {    Freq() int}type HuffmanLeaf struct {    freq  int    value rune}type HuffmanNode struct {    freq        int    left, right HuffmanTree}func (self HuffmanLeaf) Freq() int {    return self.freq}func (self HuffmanNode) Freq() int {    return self.freq}type treeHeap []HuffmanTreefunc (th treeHeap) Len() int { return len(th) }func (th treeHeap) Less(i, j int) bool {    return th[i].Freq() < th[j].Freq()}func (th *treeHeap) Push(ele interface{}) {    *th = append(*th, ele.(HuffmanTree))}func (th *treeHeap) Pop() (popped interface{}) {    popped = (*th)[len(*th)-1]    *th = (*th)[:len(*th)-1]    return}func (th treeHeap) Swap(i, j int) { th[i], th[j] = th[j], th[i] }// The main function that builds a Huffman Tree and print codes by traversing// the built Huffman Treefunc buildTree(symFreqs map[rune]int) HuffmanTree {    var trees treeHeap    for c, f := range symFreqs {        trees = append(trees, HuffmanLeaf{f, c})    }    heap.Init(&trees)    for trees.Len() > 1 {        // two trees with least frequency        a := heap.Pop(&trees).(HuffmanTree)        b := heap.Pop(&trees).(HuffmanTree)        // put into new node and re-insert into queue        heap.Push(&trees, HuffmanNode{a.Freq() + b.Freq(), a, b})    }    return heap.Pop(&trees).(HuffmanTree)}// Prints huffman codes from the root of Huffman Tree.  It uses byte[] to// store codesfunc printCodes(tree HuffmanTree, prefix []byte) {    switch i := tree.(type) {    case HuffmanLeaf:        // If this is a leaf node, then it contains one of the input        // characters, print the character and its code from byte[]        fmt.Printf("%c\t%d\t%s\n", i.value, i.freq, string(prefix))    case HuffmanNode:        // Assign 0 to left edge and recur        prefix = append(prefix, '0')        printCodes(i.left, prefix)        prefix = prefix[:len(prefix)-1]        // Assign 1 to right edge and recur        prefix = append(prefix, '1')        printCodes(i.right, prefix)        prefix = prefix[:len(prefix)-1]    }}// Driver program to test above functionsfunc main() {    test := "abcdefghijklmnopqrstuvwxyz"    symFreqs := make(map[rune]int)    // read each symbol and record the frequencies    for _, c := range test {        symFreqs[c]++    }    // example tree    exampleTree := buildTree(symFreqs)    // print out results    fmt.Println("SYMBOL\tWEIGHT\tHUFFMAN CODE")    printCodes(exampleTree, []byte{})}