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day06.go
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day06.go
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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package day06 solves AoC 2020 day 6.
package day06
import (
"strings"
"github.com/fis/aoc/glue"
)
func init() {
glue.RegisterSolver(2020, 6, glue.ChunkSolver(solve))
}
func solve(data []string) ([]string, error) {
answers := make([][]answerSet, len(data))
for i, chunk := range data {
lines := strings.Split(strings.TrimSpace(chunk), "\n")
answers[i] = parseGroup(lines)
}
var any, all int
for _, a := range answers {
any += countMerged(a, mergeAny)
all += countMerged(a, mergeAll)
}
return glue.Ints(any, all), nil
}
type answerSet [26]bool
func parseGroup(lines []string) (answers []answerSet) {
for _, s := range lines {
answers = append(answers, parseAnswerSet(s))
}
return answers
}
func parseAnswerSet(s string) (answers answerSet) {
for _, c := range s {
if c >= 'a' && c <= 'z' {
answers[c-'a'] = true
}
}
return answers
}
func countMerged(answers []answerSet, merger func([]answerSet) answerSet) (count int) {
merged := merger(answers)
for _, a := range merged {
if a {
count++
}
}
return count
}
func mergeAny(in []answerSet) (out answerSet) {
for _, answers := range in {
for i, a := range answers {
out[i] = out[i] || a
}
}
return out
}
func mergeAll(in []answerSet) (out answerSet) {
for i := range out {
out[i] = true
}
for _, answers := range in {
for i, a := range answers {
out[i] = out[i] && a
}
}
return out
}