From d2699dfd2437d2bce8432f2cd4e5e6551053b4b3 Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Sun, 5 Dec 2021 14:45:08 -0500
Subject: [PATCH] use a single slice instead of two

---
 05/main.go | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/05/main.go b/05/main.go
index 51d04fa..138fd80 100644
--- a/05/main.go
+++ b/05/main.go
@@ -42,15 +42,12 @@ type point struct {
 }
 
 type grid struct {
-	m [][]int
+	m []int
 }
 
 func (g *grid) AddLine(start, end point, includeHorizontal bool) {
 	for _, p := range LineFromPoints(start, end, includeHorizontal) {
-		if g.m[p.x] == nil {
-			g.m[p.x] = make([]int, 1000)
-		}
-		g.m[p.x][p.y]++
+		g.m[p.x+p.y*1000]++
 	}
 }
 
@@ -112,7 +109,7 @@ func partOne() {
 	scanner := makeScanner(false)
 
 	grid := &grid{
-		m: make([][]int, 1000),
+		m: make([]int, 1_000_000),
 	}
 	for scanner.Scan() {
 		line := scanner.Text()
@@ -121,10 +118,8 @@ func partOne() {
 	}
 	var danger int
 	for i := range grid.m {
-		for j := range grid.m[i] {
-			if grid.m[i][j] > 1 {
-				danger++
-			}
+		if grid.m[i] > 1 {
+			danger++
 		}
 	}
 	fmt.Println(danger)
@@ -134,7 +129,7 @@ func partTwo() {
 	scanner := makeScanner(false)
 
 	grid := &grid{
-		m: make([][]int, 1000),
+		m: make([]int, 1_000_000),
 	}
 	for scanner.Scan() {
 		line := scanner.Text()
@@ -143,10 +138,8 @@ func partTwo() {
 	}
 	var danger int
 	for i := range grid.m {
-		for j := range grid.m[i] {
-			if grid.m[i][j] > 1 {
-				danger++
-			}
+		if grid.m[i] > 1 {
+			danger++
 		}
 	}
 	fmt.Println(danger)