2021 Day 3 Complete!

2021/day03/main.go

@@ -0,0 +1,136 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	part1(inp)
+	part2(inp)
+}
+
+func binStrToUint64(inp string) uint64 {
+	var res uint64
+	for i := range inp {
+		if inp[i] == '0' {
+			res = res << 1
+		} else {
+			res = (res << 1) | 1
+		}
+	}
+	return res
+}
+
+type Pair struct {
+	zero int
+	one  int
+}
+
+func (p Pair) MostByte(fallback byte) byte {
+	if p.zero == p.one {
+		return fallback
+	} else if p.zero > p.one {
+		return '0'
+	}
+	return '1'
+}
+func (p Pair) LeastByte(fallback byte) byte {
+	if p.zero == p.one {
+		return fallback
+	} else if p.zero < p.one {
+		return '0'
+	}
+	return '1'
+}
+
+func buildReport(inp []string) map[int]Pair {
+	totals := make(map[int]Pair)
+	for k := range inp {
+		for i := range inp[k] {
+			var p Pair
+			var ok bool
+			if p, ok = totals[i]; !ok {
+				p = Pair{zero: 0, one: 0}
+			}
+			if inp[k][i] == '0' {
+				p.zero++
+			} else {
+				p.one++
+			}
+			totals[i] = p
+		}
+	}
+	return totals
+}
+
+func part1(inp []string) {
+	totals := buildReport(inp)
+	var gamma uint64
+	var epsilon uint64
+	var gammaStr string
+	var epsilonStr string
+	for i := 0; i <= len(inp[0]); i++ {
+		p, ok := totals[i]
+		if ok {
+			if p.zero > p.one {
+				//gamma = gamma << 1
+				//epsilon = (epsilon << 1) | 1
+				gammaStr = gammaStr + "0"
+				epsilonStr = epsilonStr + "1"
+			} else {
+				//gamma = (gamma << 1) | 1
+				//epsilon = epsilon << 1
+				gammaStr = gammaStr + "1"
+				epsilonStr = epsilonStr + "0"
+			}
+		}
+	}
+	gamma = binStrToUint64(gammaStr)
+	epsilon = binStrToUint64(epsilonStr)
+	fmt.Println("# Part 1")
+	fmt.Println("gamma:", gammaStr, gamma)
+	fmt.Println("epsilon:", epsilonStr, epsilon)
+	fmt.Println("power consumption:", (gamma * epsilon))
+	fmt.Println("")
+}
+
+func part2(inp []string) {
+	fmt.Println("# Part 2")
+
+	bldOx := make([]string, len(inp))
+	copy(bldOx, inp)
+	idx := 0
+	for len(bldOx) > 1 && idx < len(inp[0]) {
+		totals := buildReport(bldOx)
+		var next []string
+		for i := range bldOx {
+			if bldOx[i][idx] == totals[idx].MostByte('1') {
+				next = append(next, bldOx[i])
+			}
+		}
+		bldOx = next
+		idx++
+	}
+	oxV := binStrToUint64(bldOx[0])
+	fmt.Println("Oxygen Rating:", bldOx, oxV)
+	co2 := make([]string, len(inp))
+	copy(co2, inp)
+	idx = 0
+	for len(co2) > 1 && idx < len(inp[0]) {
+		totals := buildReport(co2)
+		var next []string
+		for i := range co2 {
+			if co2[i][idx] == totals[idx].LeastByte('0') {
+				next = append(next, co2[i])
+			}
+		}
+		co2 = next
+		idx++
+	}
+	co2V := binStrToUint64(co2[0])
+	fmt.Println("CO2 Rating:", co2, co2V)
+	fmt.Println("Life Support Rating:", (oxV * co2V))
+}

2021/day03/testinput

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010