From 0f07ffcc0054f712adf8bd955578fc240dae3017 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Wed, 15 Dec 2021 22:11:02 -0500
Subject: [PATCH] day 15 part 1 works. part 2 works on the sample, not the real
 input.

---
 15/main.go | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 15/main.go

diff --git a/15/main.go b/15/main.go
new file mode 100644
index 0000000..6b87f9f
--- /dev/null
+++ b/15/main.go
@@ -0,0 +1,128 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+)
+
+func mustAtoi(line string) int {
+	i, _ := strconv.Atoi(line)
+	return i
+}
+
+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)
+}
+
+type room struct {
+	row      int
+	col      int
+	distance int
+	cost     int
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+
+	grid := [100][100]room{}
+	col := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		for row, v := range line {
+			r := room{
+				distance: 1000,
+				cost:     mustAtoi(string(v)),
+			}
+			grid[row][col] = r
+		}
+		col++
+	}
+	grid[0][0].distance = 0
+
+	for row := 0; row < 100; row++ {
+		for col := 0; col < 100; col++ {
+			if col+1 < 100 {
+				d := grid[row][col+1].distance
+				// if the cost of the space is less than the current known distance, this is the best route there
+				if d > grid[row][col+1].cost+grid[row][col].distance {
+					grid[row][col+1].distance = grid[row][col].distance + grid[row][col+1].cost
+				}
+			}
+			if row+1 < 100 {
+				d := grid[row+1][col].distance
+				// if the cost of the space is less than the current known distance, this is the best route there
+				if d > grid[row+1][col].cost+grid[row][col].distance {
+					grid[row+1][col].distance = grid[row][col].distance + grid[row+1][col].cost
+				}
+			}
+		}
+	}
+	fmt.Println(grid[99][99].distance)
+}
+
+func partTwo() {
+	scanner := makeScanner(false)
+	width := 100
+	scale := 5
+	len := width * scale
+
+	grid := [500][500]room{}
+	col := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		for row, v := range line {
+			for i := 0; i < scale; i++ {
+				for j := 0; j < scale; j++ {
+					cost := mustAtoi(string(v)) + i + j
+					if cost > 9 {
+						cost = ((mustAtoi(string(v)) + i + j) % 10) + 1
+					}
+					grid[row+i*width][col+j*width] = room{
+						row:      row + i*width,
+						col:      col + j*width,
+						distance: 100000,
+						cost:     cost,
+					}
+				}
+			}
+		}
+		col++
+	}
+	grid[0][0].distance = 0
+
+	for row := 0; row < len; row++ {
+		for col := 0; col < len; col++ {
+			// if the cost of the space is less than the current known distance, this is the best route there
+			if col+1 < len {
+				if grid[row][col+1].distance > grid[row][col+1].cost+grid[row][col].distance {
+					grid[row][col+1].distance = grid[row][col].distance + grid[row][col+1].cost
+				}
+			}
+			if row+1 < len {
+				if grid[row+1][col].distance > grid[row+1][col].cost+grid[row][col].distance {
+					grid[row+1][col].distance = grid[row][col].distance + grid[row+1][col].cost
+				}
+			}
+		}
+	}
+	fmt.Println(grid[width*scale-1][width*scale-1])
+}