kacerrandClaude Fable 5
7219eb5a23
Includes solved 02-worker-pool and 09-safe-counter (mutex, atomic, sharded). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GbnJj9ZqEx9nUvzkjdwfMq
59 lines
1.5 KiB
Go
59 lines
1.5 KiB
Go
// Exercise 05 — LRU Cache
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//
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// ASSIGNMENT
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// ----------
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// Implement a thread-safe LRU cache:
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//
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// 1. NewLRU(capacity): holds at most `capacity` entries.
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// 2. Get(key): returns (value, true) and marks the entry most-recently-used;
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// (nil, false) on miss.
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// 3. Put(key, value): inserts or updates; updating also marks MRU.
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// When over capacity, evicts the LEAST recently used entry.
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// 4. Both operations O(1). (Hint: map + container/list, or hand-roll a
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// doubly linked list.)
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// 5. Safe for concurrent use (tests run with -race).
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//
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// Run the tests: go test -race ./05-lru-cache/
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package main
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import "fmt"
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type LRU struct {
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// TODO: fields (mutex, capacity, map[string]*list.Element, *list.List)
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// Remember: the list element must store the KEY too, or you can't
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// delete the map entry on eviction.
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}
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// NewLRU creates an LRU cache with the given capacity (capacity >= 1).
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// TODO: implement me.
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func NewLRU(capacity int) *LRU {
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return &LRU{}
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}
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// Get returns the value and whether it was present. Hit = mark MRU.
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// TODO: implement me.
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func (c *LRU) Get(key string) (any, bool) {
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return nil, false
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}
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// Put inserts/updates a value, evicting the LRU entry if over capacity.
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// TODO: implement me.
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func (c *LRU) Put(key string, val any) {
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}
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// Len returns the current number of entries.
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// TODO: implement me.
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func (c *LRU) Len() int {
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return 0
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}
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func main() {
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c := NewLRU(2)
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c.Put("a", 1)
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c.Put("b", 2)
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c.Get("a") // a is now MRU
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c.Put("c", 3) // evicts b
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_, ok := c.Get("b")
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fmt.Println("b present:", ok) // false
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}
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