From d9d802337271897a8a0ee7298a4c76c3b5f7903d Mon Sep 17 00:00:00 2001
From: arnaucube <root@arnaucube.com>
Date: Sun, 23 Feb 2020 22:26:48 +0100
Subject: [PATCH] Add codes table generation, add tests

---
 README.md       |  5 +++
 go.mod          |  8 +++++
 go.sum          | 12 +++++++
 huffman.go      | 40 ++++++++++++++++++++++
 huffman_test.go | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 153 insertions(+)
 create mode 100644 README.md
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 huffman_test.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..3aef37d
--- /dev/null
+++ b/README.md
@@ -0,0 +1,5 @@
+# huffman-coding
+
+https://en.wikipedia.org/wiki/Huffman_coding
+
+
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..7510772
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,8 @@
+module huffman-coding
+
+go 1.13
+
+require (
+	github.com/stretchr/testify v1.5.1
+	gopkg.in/go-playground/assert.v1 v1.2.1
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..83b096b
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,12 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
+github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/go-playground/assert.v1 v1.2.1 h1:xoYuJVE7KT85PYWrN730RguIQO0ePzVRfFMXadIrXTM=
+gopkg.in/go-playground/assert.v1 v1.2.1/go.mod h1:9RXL0bg/zibRAgZUYszZSwO/z8Y/a8bDuhia5mkpMnE=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/huffman.go b/huffman.go
index eba462d..d734046 100644
--- a/huffman.go
+++ b/huffman.go
@@ -90,3 +90,43 @@ func buildTree(nodes []*Node) *Node {
 	}
 	return nodes[0]
 }
+
+func descendTable(n *Node, path string, table map[byte]string) map[byte]string {
+	if n.typ == MID {
+		table = descendTable(n.l, path+"0", table)
+		table = descendTable(n.r, path+"1", table)
+	} else if n.typ == LEAF {
+		table[n.leaf] = path
+	}
+	return table
+}
+
+func generateTable(n *Node) map[byte]string {
+	table := make(map[byte]string)
+	table = descendTable(n, "", table)
+	return table
+}
+
+func Huffman(b []byte) error {
+	// compute frequencies
+	values := make(map[byte]int64)
+	for _, v := range b {
+		values[v]++
+	}
+	leafs := leafsFromValues(values)
+
+	// sort frequencies
+	sortedLeafs := sortNodes(leafs)
+
+	// build binary tree
+	n := buildTree(sortedLeafs)
+	fmt.Println(n)
+
+	// get the table (binary code for each value)
+	table := generateTable(n)
+	fmt.Println(table)
+
+	// WIP
+
+	return nil
+}
diff --git a/huffman_test.go b/huffman_test.go
new file mode 100644
index 0000000..a5ca063
--- /dev/null
+++ b/huffman_test.go
@@ -0,0 +1,88 @@
+package huffman
+
+import (
+	"fmt"
+	"testing"
+
+	"gopkg.in/go-playground/assert.v1"
+)
+
+var debug = true
+
+func TestBuildTree0(t *testing.T) {
+	values := make(map[byte]int64)
+	values[65] = 3
+	values[66] = 5
+	values[67] = 6
+	values[68] = 4
+	values[69] = 2
+
+	leafs := leafsFromValues(values)
+	sortedLeafs := sortNodes(leafs)
+	n := buildTree(sortedLeafs)
+
+	/*
+		Expected result (both valid):
+			         20
+				/  \
+			       9    \
+			      / \    \
+			     /   5    11
+		            /  	/ \   / \
+			   4   2   3  5  6
+
+			         20
+				/  \
+			       /    11
+			      /     / \
+			     9     5   \
+		            / \   / \   \
+			   4   5 2  3    6
+		The second tree is what is genereated in this test
+	*/
+	assert.Equal(t, int64(20), n.key)
+	assert.Equal(t, int64(9), n.l.key)
+	assert.Equal(t, int64(4), n.l.l.key)
+	assert.Equal(t, int64(5), n.l.r.key)
+	assert.Equal(t, int64(11), n.r.key)
+	assert.Equal(t, int64(5), n.r.l.key)
+	assert.Equal(t, int64(2), n.r.l.l.key)
+	assert.Equal(t, int64(3), n.r.l.r.key)
+	assert.Equal(t, int64(6), n.r.r.key)
+}
+
+func TestBuildTree1(t *testing.T) {
+	values := make(map[byte]int64)
+	values[97] = 10
+	values[101] = 15
+	values[105] = 12
+	values[115] = 3
+	values[116] = 4
+	values[112] = 13
+	values[10] = 1
+
+	leafs := leafsFromValues(values)
+	sortedLeafs := sortNodes(leafs)
+	n := buildTree(sortedLeafs)
+
+	assert.Equal(t, int64(58), n.key)
+	assert.Equal(t, int64(25), n.l.key)
+	assert.Equal(t, int64(33), n.r.key)
+}
+
+func TestGenerateTable(t *testing.T) {
+	values := make(map[byte]int64)
+	values[65] = 3
+	values[66] = 5
+	values[67] = 6
+	values[68] = 4
+	values[69] = 2
+
+	leafs := leafsFromValues(values)
+	sortedLeafs := sortNodes(leafs)
+	n := buildTree(sortedLeafs)
+
+	table := generateTable(n)
+
+	fmt.Println(table)
+}