2025 Day 9 Complete!

2025/day09/main.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	part1(inp)
+	fmt.Println()
+	part2(inp)
+}
+
+func part1(inp []string) {
+	c := parse(inp)
+	var largest int
+	for i := range c {
+		for j := range c[i:] {
+			a := c[i].AreaTo(c[j])
+			if a > largest {
+				largest = a
+			}
+		}
+	}
+	fmt.Println("# Part 1")
+	fmt.Println(largest)
+}
+
+func part2(inp []string) {
+	c := parse(inp)
+	var areas []Area
+	for i := range c {
+		for j := i + 1; j < len(c); j++ {
+			areas = append(areas, Area{p1: c[i], p2: c[j], area: c[i].AreaTo(c[j])})
+		}
+	}
+	sort.Slice(areas, func(a, b int) bool { return areas[a].area > areas[b].area })
+
+	var edges []h.Coordinate
+	for i := range c {
+		var t, n h.Coordinate
+		t = c[i]
+		if i < len(c)-1 {
+			n = c[i+1]
+		} else if i == len(c)-1 {
+			n = c[0]
+		}
+		edges = append(edges, getEdges(t, n)...)
+	}
+
+	var j int
+	h.PrintProgress(j, len(areas))
+	for j = 0; j < len(areas); j++ {
+		h.ClearProgress()
+		h.PrintProgress(j, len(areas))
+		var nope bool
+		for _, e := range edges {
+			if pointIn(e, areas[j]) {
+				nope = true
+				break
+			}
+		}
+		if nope {
+			continue
+		}
+		break
+	}
+	fmt.Println("# Part 2")
+	fmt.Println(areas[j].area)
+}
+
+func getEdges(c1, c2 h.Coordinate) []h.Coordinate {
+	var ret []h.Coordinate
+	if c1.X == c2.X {
+		for y := h.Min(c1.Y, c2.Y); y <= h.Max(c1.Y, c2.Y); y++ {
+			ret = append(ret, h.Coordinate{X: c1.X, Y: y})
+		}
+		return ret
+	}
+	for x := h.Min(c1.X, c2.X); x <= h.Max(c1.X, c2.X); x++ {
+		ret = append(ret, h.Coordinate{X: x, Y: c1.Y})
+	}
+	return ret
+}
+
+func parse(inp []string) []h.Coordinate {
+	var allCoords []h.Coordinate
+	for i := range inp {
+		c := h.Coordinate{}
+		fmt.Sscanf(inp[i], "%d,%d", &c.X, &c.Y)
+		allCoords = append(allCoords, c)
+	}
+	return allCoords
+}
+
+type Area struct {
+	p1, p2 h.Coordinate
+	area   int
+}
+
+// pointIn returns true if 't' is within the rectangle made
+// by Area
+func pointIn(t h.Coordinate, a Area) bool {
+	return t.X < h.Max(a.p1.X, a.p2.X) && t.X > h.Min(a.p1.X, a.p2.X) &&
+		t.Y < h.Max(a.p1.Y, a.p2.Y) && t.Y > h.Min(a.p1.Y, a.p2.Y)
+}