btree: avoid duplication of keys

btree/btree.go

@@ -86,7 +86,11 @@ func (t *Tree) Search(k string) (string, error) {
 		return "", fmt.Errorf("The key %s does not exist", k)
 	}
 
-	return t.root.search(&data{key: k})
+	if n, i := t.root.search(&data{key: k}); n != nil {
+		return n.keys[i].value, nil
+	}
+
+	return "", fmt.Errorf("The key %s does not exist", k)
 }
 
 // Remove k in the tree
@@ -123,11 +127,17 @@ func (t *Tree) Insert(key, value string) {
 	// If the tree is empty
 	if t.root == nil {
 		t.root = newNode(t.degree, true)
-		t.root.insertKey(0, k)
+		t.root.writeKey(0, k)
 		t.root.numberOfKeys = 1
 		return
 	}
 
+	// Search for an existing key and replace it
+	if node, i := t.root.search(k); node != nil {
+		node.writeKey(i, k)
+		return
+	}
+
 	// If the tree is not empty
 	if !t.root.isFull() {
 		// If root is not full, insert in non full root
@@ -158,8 +168,8 @@ func (t *Tree) Insert(key, value string) {
 
 // node methods
 
-// insertKey at i place in the node
-func (n *node) insertKey(i int, k *data) {
+// writeKey at i place in the node
+func (n *node) writeKey(i int, k *data) {
 	n.keys[i] = k
 }
 
@@ -192,7 +202,7 @@ func (n *node) visualize(prefix string, isEnd bool) {
 // traverse all nodes in a subtree rooted with this node
 func (n *node) traverse() {
 
-	// There are n entries and n+1 children, treverse trough n keys and n first children
+	// There are n entries and n+1 children, traverse trough n keys and n first children
 	for i := 0; i < n.numberOfKeys; i++ {
 		// If this is not a leaf, then traverse the subtree before printing the key
 		if !n.isLeaf {
@@ -208,7 +218,7 @@ func (n *node) traverse() {
 }
 
 // search k in the subtree rooted with this node
-func (n *node) search(k *data) (string, error) {
+func (n *node) search(k *data) (*node, int) {
 
 	// Find the first entry greater than or equal to k
 	i := 0
@@ -217,16 +227,16 @@ func (n *node) search(k *data) (string, error) {
 	}
 
 	// If the found key is equal to k, return this node
-	if n.keys[i] != nil && k.eq(n.keys[i]) {
-		return n.keys[i].value, nil
+	if i < n.numberOfKeys && k.eq(n.keys[i]) {
+		return n, i
 	}
 
 	// If the key is not found here and this is a leaf node
 	if n.isLeaf {
-		return "", fmt.Errorf("The key %s does not exist", k.key)
+		return nil, -1
 	}
 
-	// Go to the approipriate child
+	// Go to the appropriate child
 	return n.children[i].search(k)
 }
 
@@ -249,24 +259,24 @@ func (n *node) insertNonFull(k *data) {
 		}
 
 		// Insert the new key at the found location
-		n.insertKey(i+1, k)
+		n.writeKey(i+1, k)
 		n.numberOfKeys++
 		return
 	}
 
 	// If this is not a leaf
-	// Finds the child wich is going to have the new key
+	// Finds the child which is going to have the new key
 	for i >= 0 && n.keys[i].gt(k) {
 		i--
 	}
 
-	// Check if the found chird is full
+	// Check if the found child is full
 	if n.children[i+1].isFull() {
 		// If the child is full, then split it
 		n.splitChild(i+1, n.children[i+1])
 
 		// After the split, the middle key of children[i] goes up and
-		// children[i] is splitted into two
+		// children[i] is splited into two
 		// See which of those two is going to have the new key
 		if n.keys[i+1].lt(k) {
 			i++
@@ -352,7 +362,7 @@ func (n *node) remove(k *data) error {
 		isInLastChild = true
 	}
 
-	// If the child where is the key has less than t keys, wi fill it
+	// If the child where is the key has less than t keys, we fill it
 	if n.children[index].numberOfKeys < n.degree {
 		n.fill(index)
 	}

btree/btree_test.go

@@ -84,7 +84,7 @@ func ExampleTree_Traverse() {
 	tree := NewBtree(3)
 
 	toInsert := [][]string{
-		[]string{"a", "A"},
+		[]string{"a", "C"},
 		[]string{"b", "B"},
 		[]string{"c", "C"},
 		[]string{"d", "D"},
@@ -106,6 +106,8 @@ func ExampleTree_Traverse() {
 		tree.Insert(k[0], k[1])
 	}
 
+	tree.Insert("a", "A")
+
 	tree.Visualize()
 	fmt.Println("")
 

main.go

@@ -10,17 +10,14 @@ func main() {
 
 	// Example program
 	t := btree.NewBtree(3)
-	t.Insert("animal", "dog")
+	toInsert := [][]string{[]string{"climate", "change"}, []string{"machine", "doing"}, []string{"remember", "built"}, []string{"interest", "enjoy"}, []string{"no", "duty"}, []string{"contrast", "zoo"}, []string{"alike", "adventure"}, []string{"neck", "corn"}, []string{"union", "bark"}, []string{"elephant", "length"}, []string{"major", "light"}, []string{"interior", "camp"}, []string{"wind", "until"}, []string{"particles", "final"}, []string{"problem", "east"}, []string{"iron", "pattern"}, []string{"age", "personal"}, []string{"opportunity", "frog"}, []string{"goose", "sort"}, []string{"action", "effect"}, []string{"prevent", "stop"}, []string{"planned", "my"}, []string{"suit", "stood"}, []string{"orange", "forth"}, []string{"obtain", "door"}, []string{"list", "sink"}, []string{"official", "telephone"}, []string{"forest", "string"}, []string{"shade", "globe"}, []string{"city", "fighting"}, []string{"mixture", "line"}, []string{"mouth", "stomach"}, []string{"charge", "among"}, []string{"shorter", "spend"}, []string{"scale", "giant"}, []string{"spite", "image"}, []string{"evidence", "view"}, []string{"nobody", "hunter"}, []string{"cent", "recognize"}, []string{"everywhere", "avoid"}, []string{"handle", "influence"}, []string{"missing", "soft"}, []string{"strange", "seed"}, []string{"carry", "itself"}, []string{"route", "thought"}, []string{"about", "song"}, []string{"browserling", "compass"}, []string{"fort", "led"}, []string{"origin", "through"}, []string{"cover", "exciting"}, []string{"joined", "rod"}, []string{"dress", "highest"}, []string{"differ", "hall"}, []string{"slope", "discuss"}, []string{"fuel", "themselves"}, []string{"am", "final"}, []string{"straight", "constantly"}, []string{"eager", "carry"}, []string{"represent", "telephone"}, []string{"early", "something"}, []string{"young", "wagon"}, []string{"them", "late"}, []string{"space", "late"}, []string{"until", "industry"}, []string{"weigh", "president"}, []string{"fly", "power"}, []string{"average", "attempt"}, []string{"present", "rhyme"}, []string{"dear", "vowel"}, []string{"pay", "future"}, []string{"remarkable", "usual"}, []string{"brass", "type"}, []string{"blood", "began"}, []string{"size", "cat"}, []string{"around", "because"}, []string{"direction", "creature"}, []string{"lie", "blind"}, []string{"scientist", "effort"}, []string{"hardly", "dried"}, []string{"own", "fact"}, []string{"say", "direction"}, []string{"highest", "stronger"}, []string{"wait", "gently"}, []string{"old", "highway"}, []string{"eight", "four"}, []string{"active", "bread"}, []string{"square", "show"}, []string{"neighborhood", "cloud"}, []string{"flew", "separate"}, []string{"occur", "tower"}, []string{"forty", "heading"}, []string{"control", "move"}, []string{"carried", "interior"}, []string{"total", "found"}, []string{"strike", "nearby"}, []string{"mind", "talk"}, []string{"letter", "cost"}, []string{"theory", "stepped"}, []string{"remain", "fifteen"}, []string{"newspaper", "hot"}, []string{"beautiful", "arrive"}, []string{"compound", "stock"}, []string{"native", "putting"}, []string{"nodded", "sentence"}, []string{"more", "event"}, []string{"load", "nodded"}, []string{"aboard", "nation"}, []string{"continent", "work"}, []string{"buffalo", "locate"}, []string{"hunt", "outline"}, []string{"wealth", "till"}, []string{"smoke", "its"}, []string{"pair", "swim"}, []string{"necessary", "border"}, []string{"leaf", "label"}, []string{"round", "production"}, []string{"our", "wide"}, []string{"stairs", "trade"}, []string{"known", "plus"}, []string{"chose", "stronger"}, []string{"ear", "flame"}, []string{"pride", "spring"}, []string{"plates", "two"}, []string{"accurate", "sister"}, []string{"learn", "music"}, []string{"wrong", "gold"}, []string{"climate", "coffee"}, []string{"traffic", "fence"}, []string{"maybe", "aid"}, []string{"pilot", "spent"}, []string{"look", "silver"}, []string{"stretch", "book"}, []string{"back", "tea"}, []string{"wherever", "before"}, []string{"verb", "indeed"}, []string{"enemy", "bush"}, []string{"current", "may"}, []string{"be", "cover"}, []string{"task", "seldom"}, []string{"help", "typical"}, []string{"moon", "during"}, []string{"arm", "come"}, []string{"event", "shape"}, []string{"she", "needs"}, []string{"never", "nobody"}, []string{"couple", "corn"}, []string{"chance", "see"}, []string{"decide", "country"}, []string{"community", "adjective"}, []string{"none", "disappear"}, []string{"grandfather", "talk"}, []string{"white", "tank"}, []string{"attention", "early"}, []string{"sand", "score"}, []string{"speed", "friendly"}, []string{"however", "typical"}, []string{"mix", "medicine"}, []string{"support", "dozen"}, []string{"swim", "ahead"}, []string{"little", "most"}, []string{"still", "recent"}, []string{"anyone", "slipped"}, []string{"explore", "gold"}, []string{"coast", "thousand"}, []string{"written", "gather"}, []string{"heart", "somewhere"}, []string{"yard", "means"}, []string{"being", "at"}, []string{"pine", "repeat"}, []string{"kill", "rope"}, []Line truncated
 
+	for _, k := range toInsert {
+		t.Insert(k[0], k[1])
+	}
 	s, _ := t.Search("animal")
 	fmt.Println(s)
 
-	t.Insert("potato", "fries")
-	t.Insert("6", "number")
-	t.Insert("12", "number")
-	t.Insert("car", "ferrari")
-	t.Insert("7", "number")
-	t.Insert("plane", "airbus")
 	t.Insert("animal", "cat")
 
 	s, _ = t.Search("animal")