Back to home

Go Linked List main image

Go Linked List

Basic unidirectional linked lists with Golang.

Setting up the test

Set up linked_list_test.go with the following file:

package linkedlist import ( "testing" ) func TestInsertFirst(t *testing.T) { for _, tt := range insertFirstTestCases { t.Log(tt.description) l := List{} l.insertFirst(&tt.input) if tt.expectedLen != l.size { t.Errorf("FAIL: Return value expected %d but got %d", tt.expectedLen, l.size) return } if tt.expectedData != l.head.data { t.Errorf("FAIL: Return value expected %d but got %d", tt.expectedData, l.head.data) return } hasNext := l.head.next != nil if tt.expectedNext != hasNext { t.Errorf("FAIL: Return value expected %d but got %d", tt.expectedData, l.head.data) return } t.Logf("PASS: Expected length %d and got %d", tt.expectedLen, l.size) t.Logf("PASS: Expected data %d and got %d", tt.expectedData, l.head.data) t.Logf("PASS: Expected data %t and got %t", tt.expectedNext, hasNext) } } func TestInsertFirstFromArray(t *testing.T) { l := List{} n1 := Node{data: 12} n2 := Node{data: 2} n3 := Node{data: 8} l.insertFirst(&n1) l.insertFirst(&n2) l.insertFirst(&n3) if &n3 != l.head { t.Errorf("FAIL: First list value expected %+v but got %+v", &n3, l.head) return } t.Logf("PASS: First list value expected %+v but got %+v", &n3, l.head) } func TestInsertLastFromArray(t *testing.T) { l := List{} n1 := Node{data: 12} n2 := Node{data: 2} n3 := Node{data: 8} l.insertLast(&n1) l.insertLast(&n2) l.insertLast(&n3) last := l.getLast() if &n3 != last { t.Errorf("FAIL: Last list value expected %+v but got %+v", &n3, l.head) return } t.Logf("PASS: Last list value expected %+v but got %+v", &n3, l.head) } func TestGetFirst(t *testing.T) { for _, tt := range getFirstTestCases { t.Log(tt.description) l := List{} l.insertFirst(&tt.input) firstNode := l.getFirst() if firstNode != &tt.input { t.Errorf("FAIL: Return value expected %+v but got %+v", &tt.input, firstNode) return } t.Logf("PASS: Expected %+v and got %+v", &tt.input, firstNode) } } func TestClearList(t *testing.T) { l := List{} n1 := Node{data: 12} n2 := Node{data: 2} n3 := Node{data: 8} l.insertLast(&n1) l.insertLast(&n2) l.insertLast(&n3) l.clear() if l.head != nil { t.Errorf("FAIL: Last list value expected nil but got %+v", l.head) return } t.Logf("PASS: Last list value expected nil and got %+v", l.head) } func TestGetNodeAtIndexOfList(t *testing.T) { l := List{} n1 := Node{data: 12} n2 := Node{data: 2} n3 := Node{data: 8} l.insertLast(&n1) l.insertLast(&n2) l.insertLast(&n3) res, err := l.getAt(1) if err != nil { t.Errorf("FAIL: Return error from GetNodeAtIndex") return } if &n2 != res { t.Errorf("FAIL: Get list value expected %+v but got %+v", &n2, res) return } t.Logf("PASS: Get list value expected %+v and got %+v", &n2, res) } func TestRemoveNodeAtIndexOfList(t *testing.T) { l := List{} n1 := Node{data: 12} n2 := Node{data: 2} n3 := Node{data: 8} l.insertLast(&n1) l.insertLast(&n2) l.insertLast(&n3) err := l.removeAt(1) res, getErr := l.getAt(1) if err != nil { t.Errorf("FAIL: Return error from GetNodeAtIndex") return } if getErr != nil { t.Errorf("FAIL: Return error from GetNodeAtIndex") return } if &n3 != res { t.Errorf("FAIL: Post-removed list value expected %+v but got %+v", &n3, res) return } t.Logf("PASS: Post-removed list value expected %+v and got %+v", &n3, res) } func TestInsertNodeAtIndexOfList(t *testing.T) { l := List{} n1 := Node{data: 12} n2 := Node{data: 2} n3 := Node{data: 8} n4 := Node{data: 123} l.insertLast(&n1) l.insertLast(&n2) l.insertLast(&n3) err := l.insertAt(1, &n4) if err != nil { t.Errorf("FAIL: Return error from GetNodeAtIndex") return } res, getErr := l.getAt(1) if getErr != nil { t.Errorf("FAIL: Return error from GetNodeAtIndex") return } if &n4 != res { t.Errorf("FAIL: Insert list value expected %+v but got %+v", &n4, res) return } t.Logf("PASS: Insert list value expected %+v and got %+v", &n4, res) }

Trees implementation

/* @author Dennis O'Keeffe Methods: 1. insertFirst: Insert at the head of list 2. size: Fetch size 3. getFirst: Fetch the first node 4. getLast: Fetch the last node 5. clear: Remove all node 6. removeFirst: Remove head of list 7. removeLast: Remove last node 8. insertLast: Insert at end of list 9. getAt: Fetch node at index 10. removeAt: Remove node at index 11. insertAt: Insert at index 12. forEach: Iterate through list and run function on list */ package linkedlist import ( "errors" "sync" ) // Node - Setup base node type for linked list type Node struct { data int next *Node } // List - Basic singularly linked list type List struct { head *Node size int lock sync.Mutex } func (l *List) insertFirst(n *Node) { l.lock.Lock() if l.head != nil { tmp := l.head l.head = n n.next = tmp } else { l.head = n } l.size++ l.lock.Unlock() } func (l *List) insertLast(n *Node) { l.lock.Lock() if l.head == nil { l.head = n } else { last := l.head for { if last.next == nil { break } last = last.next } last.next = n } l.size++ l.lock.Unlock() } func (l *List) getFirst() *Node { return l.head } func (l *List) getLast() *Node { l.lock.Lock() n := l.head for { if n.next == nil { break } n = n.next } l.lock.Unlock() return n } func (l *List) clear() { l.lock.Lock() l.head = nil l.lock.Unlock() } func (l *List) getAt(index int) (*Node, error) { if l.head == nil { return nil, errors.New("No elements in list") } l.lock.Lock() i := 0 n := l.head for { if i == index { break } if n.next == nil { return nil, errors.New("No elements in list") } i++ n = n.next } l.lock.Unlock() return n, nil } func (l *List) removeAt(index int) error { if l.head == nil { return errors.New("No elements at index found in list") } l.lock.Lock() n := l.head i := 0 for { if i == index-1 { tmp := n.next.next n.next = tmp break } if n.next == nil { return errors.New("Out of range") } n = n.next } l.lock.Unlock() return nil } func (l *List) insertAt(index int, node *Node) error { if l.head == nil { return errors.New("No elements at index found in list") } l.lock.Lock() n := l.head i := 0 for { if i == index-1 { tmp := n.next.next n.next = node node.next = tmp break } if n.next == nil { return errors.New("Out of range") } n = n.next } l.lock.Unlock() return nil }

Running Tests

In the directory, run go test.

Personal image

Dennis O'Keeffe

@dennisokeeffe92
  • Melbourne, Australia

Hi, I am a professional Software Engineer. Formerly of Culture Amp, UsabilityHub, Present Company and NightGuru.
I am currently working on workingoutloud.dev, Den Dribbles and LandPad .

1,200+ PEOPLE ALREADY JOINED ❤️️

Get fresh posts + news direct to your inbox.

No spam. We only send you relevant content.