Implement 2021/day03 puzzle solution (#60)

* feat: Add 2021/day03 puzzle specs and test

* feat: Register 2021/day03 puzzle

* fix: Register issue

* feat: Implement 2021/day03 part1

* tests: Update regression test for 2021/day03 part1

* feat: Implement 2021/day03 part2

* tests: Add regression tests for 2021/day03

* docs: Mark 2021/day03 as solved

* fix: Sonar code smells

* style: Gofmt

Author: obalunenko

README.md

@@ -221,7 +221,7 @@ This repository contains solutions for puzzles and cli tool to run solutions to
 
   - [x] [Day 1: Sonar Sweep](https://adventofcode.com/2021/day/1)
   - [x] [Day 2: Dive!](https://adventofcode.com/2021/day/2)
-  - [ ] [Day 3: Binary Diagnostic](https://adventofcode.com/2021/day/3)
+  - [x] [Day 3: Binary Diagnostic](https://adventofcode.com/2021/day/3)
   - [ ] [Day 4: Giant Squid](https://adventofcode.com/2021/day/4)
   - [ ] [Day 5: ?](https://adventofcode.com/2021/day/5)
   - [ ] [Day 6: ?](https://adventofcode.com/2021/day/6)

internal/puzzles/solutions/2021/day03/solution.go

@@ -0,0 +1,217 @@
+// Package day03 contains solution for https://adventofcode.com/2021/day/3 puzzle.
+package day03
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+
+	"github.com/obalunenko/advent-of-code/internal/puzzles"
+)
+
+func init() {
+	puzzles.Register(solution{})
+}
+
+type solution struct{}
+
+func (s solution) Year() string {
+	return puzzles.Year2021.String()
+}
+
+func (s solution) Day() string {
+	return puzzles.Day03.String()
+}
+
+func (s solution) Part1(input io.Reader) (string, error) {
+	diagnostic, err := makeDiagnostic(input)
+	if err != nil {
+		return "", fmt.Errorf("make diagnostic report: %w", err)
+	}
+
+	r := findPowerConsumptionRates(diagnostic)
+
+	consumption, err := r.consumption()
+	if err != nil {
+		return "", fmt.Errorf("consumption calculate: %w", err)
+	}
+
+	return consumption, nil
+}
+
+func (s solution) Part2(input io.Reader) (string, error) {
+	diagnostic, err := makeDiagnostic(input)
+	if err != nil {
+		return "", fmt.Errorf("make diagnostic report: %w", err)
+	}
+
+	r := lifeSupportRate(diagnostic)
+
+	consumption, err := r.consumption()
+	if err != nil {
+		return "", fmt.Errorf("consumption calculate: %w", err)
+	}
+
+	return consumption, nil
+}
+
+func makeDiagnostic(input io.Reader) ([]string, error) {
+	scanner := bufio.NewScanner(input)
+
+	var report []string
+
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		report = append(report, line)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("scanner error: %w", err)
+	}
+
+	return report, nil
+}
+
+type bitrates struct {
+	first  string
+	second string
+}
+
+func (b bitrates) consumption() (string, error) {
+	const (
+		baseBin = 2
+		baseDec = 10
+		bitsize = 64
+	)
+
+	g, err := strconv.ParseInt(b.first, baseBin, bitsize)
+	if err != nil {
+		return "", fmt.Errorf("parse first: %w", err)
+	}
+
+	e, err := strconv.ParseInt(b.second, baseBin, bitsize)
+	if err != nil {
+		return "", fmt.Errorf("parse second: %w", err)
+	}
+
+	c := g * e
+
+	return strconv.FormatInt(c, baseDec), nil
+}
+
+type (
+	bit string
+	pos int
+)
+
+const (
+	bit0 bit = "0"
+	bit1 bit = "1"
+)
+
+func findPowerConsumptionRates(diagnostic []string) bitrates {
+	var result bitrates
+
+	bitsStat := make(map[pos]map[bit]int)
+
+	for _, s := range diagnostic {
+		for p, r := range []rune(s) {
+			if bitsStat[pos(p)] == nil {
+				bitsStat[pos(p)] = make(map[bit]int)
+			}
+
+			bitsStat[pos(p)][bit(r)]++
+		}
+	}
+
+	for i := 0; i < len(bitsStat); i++ {
+		m := bitsStat[pos(i)]
+
+		if m[bit1] > m[bit0] {
+			result.first += string(bit1)
+			result.second += string(bit0)
+		} else {
+			result.first += string(bit0)
+			result.second += string(bit1)
+		}
+	}
+
+	return result
+}
+
+func lifeSupportRate(diagnostic []string) bitrates {
+	o2 := lifeRate(diagnostic, o2Criteria)
+	co2 := lifeRate(diagnostic, co2Criteria)
+
+	return bitrates{
+		first:  o2,
+		second: co2,
+	}
+}
+
+func lifeRate(diagnostic []string, criteriaFunc bitCriteriaFunc) string {
+	var (
+		result string
+		idx    pos
+	)
+
+	for len(diagnostic) != 1 {
+		bitstat := make(map[bit]int)
+
+		for i := range diagnostic {
+			runes := []rune(diagnostic[i])
+
+			b := bit(runes[idx])
+
+			bitstat[b]++
+		}
+
+		diagnostic = filterDiagnostic(diagnostic, idx, bitstat, criteriaFunc)
+
+		idx++
+	}
+
+	result = diagnostic[0]
+
+	return result
+}
+
+type bitCriteriaFunc func(bitstat map[bit]int) bit
+
+func o2Criteria(bitstat map[bit]int) bit {
+	common := bit1
+
+	if bitstat[bit0] > bitstat[bit1] {
+		common = bit0
+	}
+
+	return common
+}
+
+func co2Criteria(bitstat map[bit]int) bit {
+	common := bit0
+
+	if bitstat[bit1] < bitstat[bit0] {
+		common = bit1
+	}
+
+	return common
+}
+
+func filterDiagnostic(diagnostic []string, idx pos, bitstat map[bit]int, bfunc bitCriteriaFunc) []string {
+	common := bfunc(bitstat)
+
+	filtered := make([]string, 0, len(diagnostic))
+
+	for i := range diagnostic {
+		runes := []rune(diagnostic[i])
+
+		if bit(runes[idx]) == common {
+			filtered = append(filtered, diagnostic[i])
+		}
+	}
+
+	return filtered
+}