Interactive DSA and system design

Learn complex engineering ideas by watching them move.

32stepsO(1)averageO(capacity)space

System Design lab

LRU Cache HashMap + DLL Flow

Step 1 / 32

HashMap Index (Quick O(1) Lookups)

null

Doubly Linked List (Ordering by Recency)

HEAD➔

Cache is Empty

➔TAIL

HashMap Reference Access / Hit (Active) Prepend (Head / MRU) Evicted Node (Tail / LRU)

Animation speed

Space play / pause←→ stepR reset

Current operation

Initialize LRU Cache

Create an empty HashMap and a Doubly Linked List with capacity 3.

Algorithm state

3Capacity0 / 3Cache Size

Interactive LRU Console

Key

Value

Operation Queue

PUT(,64)PUT(,28)PUT(,88)PUT(,12)PUT(,52)PUT(,96)PUT(,36)PUT(,72)PUT(,44)PUT(,8)

Complexity notes

O(1)averageO(1)worstO(capacity)spaceN/Astable

Synced code trace

function get(key) {  if (!map.has(key)) return null;  const node = map.get(key);  moveToHead(node);  return node.value;}function put(key, value) {  if (map.has(key)) {    const node = map.get(key);    node.value = value;    moveToHead(node);  } else {    if (map.size >= capacity) {      const tail = popTail();      map.delete(tail.key);    }    const newNode = new Node(key, value);    addToHead(newNode);    map.put(key, newNode);  }}

Interactive Notes

✓ Notes are saved automatically and persist per step.