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merkletree.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+)
+
+type MerkleTree struct {
+	Root *MerkleNode
+}
+
+type MerkleNode struct {
+	Left  *MerkleNode
+	Right *MerkleNode
+	Value []byte
+}
+
+func buildMerkleNode(left *MerkleNode, right *MerkleNode, value []byte) *MerkleNode {
+
+	newNode := MerkleNode{}
+
+	if left == nil && right == nil {
+		hash := sha256.Sum256(value)
+		newNode.Value = hash[0:]
+	} else {
+		prevHashVal := append(left.Value, right.Value...)
+		hash := sha256.Sum256(prevHashVal)
+		newNode.Value = hash[0:]
+
+	}
+
+	newNode.Left = left
+	newNode.Right = right
+
+	return &newNode
+
+}
+
+func buildMerkleTree(values [][]byte) *MerkleTree {
+	var newNodes []MerkleNode
+
+	for _, v := range values {
+		newNode := buildMerkleNode(nil, nil, v)
+		newNodes = append(newNodes, *newNode)
+	}
+
+	for len(newNodes) > 1 {
+		//checking whether the length is even or not
+		if len(newNodes)%2 == 1 {
+			newNodes = append(newNodes, newNodes[len(newNodes)-1])
+		}
+
+		//here we are changing every val in value into merkle node
+		var parentHashes []MerkleNode
+		for i := 0; i < len(newNodes); i += 2 {
+			newNode := buildMerkleNode(&newNodes[i], &newNodes[i+1], nil)
+			parentHashes = append(parentHashes, *newNode)
+		}
+		newNodes = parentHashes
+	}
+
+	//fmt.Println("new node", newNodes)
+
+	tree := MerkleTree{&newNodes[0]}
+
+	return &tree
+}
+
+func main() {
+
+	values := []string{"GeeksforGeeks", "A", "Computer", "Science", "Portal", "For", "Geeks"}
+	//values := []string{}
+	data := [][]byte{}
+
+	if len(values) == 0 {
+		fmt.Println("NO transactions")
+	} else {
+		for k, v := range values {
+			_ = k
+			a := []byte(v)
+			data = append(data, a)
+		}
+		rootHash := buildMerkleTree(data)
+		fmt.Println("Root hash", hex.EncodeToString(rootHash.Root.Value))
+	}
+
+}