Commit c81cc26

isidroasCjkjvfnbyMaximSmolskiy

authored

Improve hash map (#12678)

* Mutable _Item * document falsy item * resize_down: expected test result * resize_down: actual result This is a problem since it causes rapid cycling * improve comment about falsy item Co-authored-by: Andrey <Cjkjvfnby@gmail.com> * fix long line * Update hash_map.py * Update hash_map.py --------- Co-authored-by: Andrey <Cjkjvfnby@gmail.com> Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>

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data_structures/hashing
- hash_map.py

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+26

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`‎data_structures/hashing/hash_map.py`

Lines changed: 26 additions & 4 deletions

Original file line number	Diff line number	Diff line change
`@@ -16,7 +16,7 @@`
`16`	`16`	`VAL = TypeVar("VAL")`
`17`	`17`
`18`	`18`
`19`		`-@dataclass(frozen=True, slots=True)`
	`19`	`+@dataclass(slots=True)`
`20`	`20`	`class _Item(Generic[KEY, VAL]):`
`21`	`21`	`key: KEY`
`22`	`22`	`val: VAL`
`@@ -72,16 +72,17 @@ def _try_set(self, ind: int, key: KEY, val: VAL) -> bool:`
`72`	`72`
`73`	`73`	`If bucket is empty or key is the same, does insert and return True.`
`74`	`74`
`75`		`- If bucket has another key or deleted placeholder,`
`76`		`- that means that we need to check next bucket.`
	`75`	`+ If bucket has another key that means that we need to check next bucket.`
`77`	`76`	`"""`
`78`	`77`	`stored = self._buckets[ind]`
`79`	`78`	`if not stored:`
	`79`	`+ # A falsy item means that bucket was never used (None)`
	`80`	`+ # or was deleted (_deleted).`
`80`	`81`	`self._buckets[ind] = _Item(key, val)`
`81`	`82`	`self._len += 1`
`82`	`83`	`return True`
`83`	`84`	`elif stored.key == key:`
`84`		`- self._buckets[ind] = _Item(key, val)`
	`85`	`+ stored.val = val`
`85`	`86`	`return True`
`86`	`87`	`else:`
`87`	`88`	`return False`
`@@ -228,6 +229,27 @@ def __delitem__(self, key: KEY) -> None:`
`228`	`229`	`Traceback (most recent call last):`
`229`	`230`	`...`
`230`	`231`	`KeyError: 4`
	`232`	`+`
	`233`	`+ # Test resize down when sparse`
	`234`	`+ ## Setup: resize up`
	`235`	`+ >>> hm = HashMap(initial_block_size=100, capacity_factor=0.75)`
	`236`	`+ >>> len(hm._buckets)`
	`237`	`+ 100`
	`238`	`+ >>> for i in range(75):`
	`239`	`+ ... hm[i] = i`
	`240`	`+ >>> len(hm._buckets)`
	`241`	`+ 100`
	`242`	`+ >>> hm[75] = 75`
	`243`	`+ >>> len(hm._buckets)`
	`244`	`+ 200`
	`245`	`+`
	`246`	`+ ## Resize down`
	`247`	`+ >>> del hm[75]`
	`248`	`+ >>> len(hm._buckets)`
	`249`	`+ 200`
	`250`	`+ >>> del hm[74]`
	`251`	`+ >>> len(hm._buckets)`
	`252`	`+ 100`
`231`	`253`	`"""`
`232`	`254`	`for ind in self._iterate_buckets(key):`
`233`	`255`	`item = self._buckets[ind]`

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Commit c81cc26

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`‎data_structures/hashing/hash_map.py`

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