add linkedlists

Author: himanshub16

data-structures/linked-list/double-linkedlist.go

@@ -0,0 +1,156 @@
+// demonstration of doubly linked list in golang
+
+package doublelinkedlist
+
+// package main
+
+import "fmt"
+
+type node struct {
+	val  int
+	next *node
+	prev *node
+}
+
+type doublelinkedlist struct {
+	head *node
+}
+
+// to avoid mistakes when using pointer vs struct for new node creation
+func newNode(val int) *node {
+	n := &node{}
+	n.val = val
+	n.next = nil
+	n.prev = nil
+	return n
+}
+
+func (ll *doublelinkedlist) addAtBeg(val int) {
+	n := newNode(val)
+	n.next = ll.head
+	ll.head = n
+}
+
+func (ll *doublelinkedlist) addAtEnd(val int) {
+	n := newNode(val)
+
+	if ll.head == nil {
+		ll.head = n
+		return
+	}
+
+	cur := ll.head
+	for ; cur.next != nil; cur = cur.next {
+	}
+	cur.next = n
+	n.prev = cur
+}
+
+func (ll *doublelinkedlist) delAtBeg() int {
+	if ll.head == nil {
+		return -1
+	}
+
+	cur := ll.head
+	ll.head = cur.next
+
+	if ll.head != nil {
+		ll.head.prev = nil
+	}
+
+	return cur.val
+}
+
+func (ll *doublelinkedlist) delAtEnd() int {
+	// no item
+	if ll.head == nil {
+		return -1
+	}
+
+	// only one item
+	if ll.head.next == nil {
+		return ll.delAtBeg()
+	}
+
+	// more than one, go to second last
+	cur := ll.head
+	for ; cur.next.next != nil; cur = cur.next {
+	}
+
+	retval := cur.next.val
+	cur.next = nil
+	return retval
+}
+
+func (ll *doublelinkedlist) count() int {
+	var ctr int = 0
+
+	for cur := ll.head; cur != nil; cur = cur.next {
+		ctr += 1
+	}
+
+	return ctr
+}
+
+func (ll *doublelinkedlist) reverse() {
+	var prev, next *node
+	cur := ll.head
+
+	for cur != nil {
+		next = cur.next
+		cur.next = prev
+		cur.prev = next
+		prev = cur
+		cur = next
+	}
+
+	ll.head = prev
+}
+
+func (ll *doublelinkedlist) display() {
+	for cur := ll.head; cur != nil; cur = cur.next {
+		fmt.Print(cur.val, " ")
+	}
+
+	fmt.Print("\n")
+}
+
+func (ll *doublelinkedlist) displayReverse() {
+	if ll.head == nil {
+		return
+	}
+	var cur *node
+	for cur = ll.head; cur.next != nil; cur = cur.next {
+	}
+
+	for ; cur != nil; cur = cur.prev {
+		fmt.Print(cur.val, " ")
+	}
+
+	fmt.Print("\n")
+}
+
+/*
+func main() {
+	ll := doublelinkedlist{}
+
+	ll.addAtBeg(10)
+	ll.addAtEnd(20)
+	ll.display()
+	ll.addAtBeg(30)
+	ll.display()
+
+	ll.reverse()
+	ll.display()
+	ll.displayReverse()
+
+	fmt.Print(ll.delAtBeg(), "\n")
+	fmt.Print(ll.delAtEnd(), "\n")
+	fmt.Print("Display")
+	ll.display()
+	fmt.Print(ll.delAtBeg(), "\n")
+	ll.display()
+	fmt.Print(ll.delAtBeg(), "\n")
+	ll.display()
+}
+*/

data-structures/linked-list/single-linkedlist.go

@@ -0,0 +1,123 @@
+// demonstration of singly linked list in golang
+
+package singlelinkedlist
+
+// package main
+
+import "fmt"
+
+type node struct {
+	val  int
+	next *node
+}
+
+type singlelinkedlist struct {
+	head *node
+}
+
+// to avoid mistakes when using pointer vs struct for new node creation
+func newNode(val int) *node {
+	return &node{val, nil}
+}
+
+func (ll *singlelinkedlist) addAtBeg(val int) {
+	n := newNode(val)
+	n.next = ll.head
+	ll.head = n
+}
+
+func (ll *singlelinkedlist) addAtEnd(val int) {
+	n := newNode(val)
+
+	if ll.head == nil {
+		ll.head = n
+		return
+	}
+
+	cur := ll.head
+	for ; cur.next != nil; cur = cur.next {
+	}
+	cur.next = n
+}
+
+func (ll *singlelinkedlist) delAtBeg() int {
+	if ll.head == nil {
+		return -1
+	}
+
+	cur := ll.head
+	ll.head = cur.next
+
+	return cur.val
+}
+
+func (ll *singlelinkedlist) delAtEnd() int {
+	if ll.head == nil {
+		return -1
+	}
+
+	if ll.head.next == nil {
+		return ll.delAtBeg()
+	}
+
+	cur := ll.head
+
+	for ; cur.next.next != nil; cur = cur.next {
+	}
+
+	retval := cur.next.val
+	cur.next = nil
+	return retval
+
+}
+
+func (ll *singlelinkedlist) count() int {
+	var ctr int = 0
+
+	for cur := ll.head; cur != nil; cur = cur.next {
+		ctr += 1
+	}
+
+	return ctr
+}
+
+func (ll *singlelinkedlist) reverse() {
+	var prev, next *node
+	cur := ll.head
+
+	for cur != nil {
+		next = cur.next
+		cur.next = prev
+		prev = cur
+		cur = next
+	}
+
+	ll.head = prev
+}
+
+func (ll *singlelinkedlist) display() {
+	for cur := ll.head; cur != nil; cur = cur.next {
+		fmt.Print(cur.val, " ")
+	}
+
+	fmt.Print("\n")
+}
+
+// func main() {
+// 	ll := singlelinkedlist{}
+
+// 	ll.addAtBeg(10)
+// 	ll.addAtEnd(20)
+// 	ll.display()
+// 	ll.addAtBeg(30)
+// 	ll.display()
+// 	ll.reverse()
+// 	ll.display()
+
+// 	fmt.Print(ll.delAtBeg(), "\n")
+// 	ll.display()
+
+// 	fmt.Print(ll.delAtEnd(), "\n")
+// 	ll.display()
+
+// }