Iddiżinja struttura personalizzata tfisser kumpożizzjoni tal-istrutturi eżistenti sabiex kull operazzjoni meħtieġa tilħaq il-komplesso tiegħa, u struttura waħda takopri d-dgħajjes ta' oħra. It-teknika klassika hija iqqabbel hash map ma' array, heap, jew linked list.
Rekwiżiti: , , u kull wieħed f'O(1). Hash map waħdu ma jistax jagħmel O(1) random; array waħdu ma jistax jagħmel O(1) remove. .
insert(x)remove(x)getRandom()import random
class RandomizedSet:
def __init__(self):
self.idx = {} # value -> index in list
self.vals = [] # values for O(1) random pick
def insert(self, x): # O(1)
if x in self.idx: return False
self.idx[x] = len(self.vals)
self.vals.append(x)
return True
def remove(self, x): # O(1): swap with last, pop
if x not in self.idx: return False
i, last = self.idx[x], self.vals[-1]
self.vals[i] = last # move last into the hole
self.idx[last] = i
self.vals.pop()
del self.idx[x]
return True
def getRandom(self): # O(1)
return random.choice(self.vals)
1. List every required operation + its target complexity.
2. For each, name a structure that hits it:
by key O(1) -> hash map
by index O(1) -> array
min/max O(log n) -> heap
ordered O(log n) -> balanced tree / skip list
O(1) splice -> doubly linked list
3. COMBINE them; use the hash map to map keys -> positions/nodes
in the other structure so updates stay O(1).
4. Verify each operation against its target.
| Pattern | Strutturi ikkombinati | Jippermettu |
|---|---|---|
| LRU cache | hash map + doubly linked list | O(1) get/put |
| O(1) randomized set | hash map + array | O(1) insert/remove/random |
| Min in O(1) on a stack | stack + auxiliary min-stack | O(1) getMin |
Sistemi reali rari għandhom bżonn struttura waħda mill-libru tad-dardir — għandhom bżonn kumpożizzjoni tatuned għall-mudell ta' aċċess spċifiku, li huwa preċiżament dak li dawn id-disinn jipprovdu.
L-intervistataturi jużaw dawn il-problemi biex itestjaw jekk tista' taħseb mir-spiża tal-operazzjonijiet għal kumpożizzjoni, il-ħiliet ewlenin wara d-diżinn tas-sistema ta' prestazzjoni għolja.