From 8e68234caa54cf0139d69f8a469b27b1bda46ec6 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Tue, 7 Dec 2021 09:19:13 -0500
Subject: [PATCH] day 7 in the books

---
 07/main.go | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 07/main.go

diff --git a/07/main.go b/07/main.go
new file mode 100644
index 0000000..d8aaa46
--- /dev/null
+++ b/07/main.go
@@ -0,0 +1,111 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
+}
+
+func makeScanner(test bool) *bufio.Scanner {
+	var f *os.File
+	if test {
+		f, _ = os.Open("inputs/testinput")
+	} else {
+		f, _ = os.Open("inputs/input")
+	}
+	reader := bufio.NewReader(f)
+	return bufio.NewScanner(reader)
+}
+
+func mustAtoi(line string) int {
+	i, _ := strconv.Atoi(line)
+	return i
+}
+
+func fuelCostPartOne(crabs []int, column int) int {
+	var totalFuel int
+	for _, v := range crabs {
+		if column < v {
+			totalFuel += v - column
+		}
+		if column > v {
+			totalFuel += column - v
+		}
+	}
+	return totalFuel
+}
+
+func fuelCostPartTwo(crabs []int, column int) int {
+	var totalFuel int
+	for _, v := range crabs {
+		if column < v {
+			totalFuel += ((v - column) * ((v - column) + 1)) / 2
+		}
+		if column > v {
+			totalFuel += ((column - v) * ((column - v) + 1)) / 2
+		}
+	}
+	return totalFuel
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+
+	// just a single line today
+	scanner.Scan()
+	input := strings.Split(scanner.Text(), ",")
+	crabs := []int{}
+	var max int
+	for _, v := range input {
+		crab := mustAtoi(v)
+		crabs = append(crabs, crab)
+		if max < crab {
+			max = crab
+		}
+	}
+	lowestFuel := 1000000000 // some initial awful max fuel cost
+	for i := 0; i <= max; i++ {
+		cost := fuelCostPartOne(crabs, i)
+		if cost < lowestFuel {
+			lowestFuel = cost
+		}
+	}
+	fmt.Println(lowestFuel)
+}
+
+func partTwo() {
+	scanner := makeScanner(false)
+
+	// just a single line today
+	scanner.Scan()
+	input := strings.Split(scanner.Text(), ",")
+	crabs := []int{}
+	var max int
+	for _, v := range input {
+		crab := mustAtoi(v)
+		crabs = append(crabs, crab)
+		if max < crab {
+			max = crab
+		}
+	}
+	lowestFuel := 1000000000 // some initial awful max fuel cost
+	for i := 0; i <= max; i++ {
+		cost := fuelCostPartTwo(crabs, i)
+		if cost < lowestFuel {
+			lowestFuel = cost
+		}
+	}
+	fmt.Println(lowestFuel)
+}