Day 10: Adapter Array

Classes:

HistogramOfDeltas(mapping)

Represent a histogram of differences between adapters in jolts.

Functions:

histogram_differences(adapters)	Compute the histogram of jolt differences in adapters.
compute_result(histo)	Analyze the histogram of jolt differences.
parse(lines)	Parse the specification of the adapters given as lines.

class HistogramOfDeltas(mapping: Mapping[int, int])

Represent a histogram of differences between adapters in jolts.

Methods:

__new__(cls, mapping)	Enforce histogram constraints.
__getitem__(key)	Retrieve the count corresponding to the histogram bin given with key.
__iter__()	Iterate over histogram bins.
__len__()	Retrieve the number of the histogram bins.

static __new__(cls, mapping: Mapping[int, int]) → HistogramOfDeltas

Enforce histogram constraints.

Requires

• all(count >= 0 for count in mapping.values())

• all(delta > 0 for delta in mapping.keys())

__getitem__(key: int) → int

Retrieve the count corresponding to the histogram bin given with key.

__iter__() → Iterator[int]

Iterate over histogram bins.

__len__() → int

Retrieve the number of the histogram bins.

histogram_differences(adapters: List[int]) → HistogramOfDeltas

Compute the histogram of jolt differences in adapters.

Requires

• len(adapters) > 0

• 0 not in adapters

  (The charging input not in adapters)

• all(adapter >= 0 for adapter in adapters)

• len(set(adapters)) == len(adapters)

Ensures

• len(adapters) == 0 ⇒ sum(result.values()) == 0

  (Empty histogram on empty input)

• sum(result.values()) == len(adapters) + 1

compute_result(histo: HistogramOfDeltas) → int

Analyze the histogram of jolt differences.

Returns

the product of the respective counts of 1s and 3s differences

Ensures

• result >= 0

parse(lines: Lines) → List[int]

Parse the specification of the adapters given as lines.

Returns

List of corresponding number of adapter jolts

Requires

• all(re.match(r"^(0|[1-9][0-9]*)Z", line) for line in lines)

Ensures

• len(lines) == len(result)