2025 Day 7 Complete!

2025/day07/main.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	part1(inp)
+	fmt.Println()
+	part2(inp)
+}
+
+func part1(inp []string) {
+	var ret int
+	m := h.StringSliceToCoordByteMap(inp)
+	ok := true
+	for ok {
+		var splits int
+		splits, ok = progBeams(&m)
+		ret += splits
+	}
+	fmt.Println("# Part 1")
+	fmt.Println(ret)
+}
+
+func progBeams(m *h.CoordByteMap) (int, bool) {
+	var splits int
+	beam, err := m.FindLast('|')
+	if err != nil {
+		beam, _ = m.FindFirst('S')
+	}
+	if beam.Y == m.BRY {
+		return 0, false
+	}
+	beams := m.FindAllOnRow(beam.Y, '|')
+	if len(beams) == 0 {
+		beams = append(beams, beam)
+	}
+
+	for i := range beams {
+		nxt := m.Get(beams[i].South())
+		switch nxt {
+		case '.':
+			m.Put(beams[i].South(), '|')
+		case '^':
+			splits++
+			m.Put(beams[i].South().East(), '|')
+			m.Put(beams[i].South().West(), '|')
+		}
+	}
+	return splits, true
+}
+
+func part2(inp []string) {
+	m := h.StringSliceToCoordByteMap(inp)
+	fmt.Println("# Part 2")
+	fmt.Println(quantumRevKickoff(&m))
+}
+
+// quantumRevKickoff starts checks for each potential beam output
+func quantumRevKickoff(m *h.CoordByteMap) int {
+	var ret int
+	var wg sync.WaitGroup
+	status := make([]byte, m.BRX)
+	for i := range status {
+		status[i] = '.'
+	}
+	track := &WorldTracker{
+		t: make(map[h.Coordinate]int),
+	}
+	for x := m.TLX; x < m.BRX; x++ {
+		c := h.Coordinate{X: x, Y: m.BRY}
+		wg.Go(func() {
+			if r, v := quantumRevCalc(m, c, track); v {
+				ret += r
+				status[c.X] = 'O'
+			} else {
+				status[c.X] = 'X'
+			}
+		})
+	}
+	wg.Wait()
+	return ret + 1
+}
+
+type WorldTracker struct {
+	t    map[h.Coordinate]int
+	lock sync.Mutex
+}
+
+func (t *WorldTracker) Get(k h.Coordinate) (int, bool) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+	v, ok := t.t[k]
+	return v, ok
+}
+func (t *WorldTracker) Set(k h.Coordinate, v int) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+	t.t[k] = v
+}
+
+// quantumRevCalc calculates how many worlds would provide a beam at
+// the given coordinate
+func quantumRevCalc(m *h.CoordByteMap, c h.Coordinate, track *WorldTracker) (int, bool) {
+	if v, ok := track.Get(c); ok {
+		return v, ok
+	}
+	var ret int
+	var valid bool
+	if m.Get(c.East()) == '^' {
+		if r, v := quantumRevCalc(m, c.East(), track); v {
+			ret += r
+			valid = true
+		}
+	}
+	if m.Get(c.West()) == '^' {
+		if r, v := quantumRevCalc(m, c.West(), track); v {
+			ret += r
+			valid = true
+		}
+	}
+	if m.Get(c.North()) == '.' {
+		if r, v := quantumRevCalc(m, c.North(), track); v {
+			ret += r
+			valid = true
+		}
+	}
+	track.Set(c, ret)
+	if m.Get(c.North()) == 'S' {
+		return 1, true
+	}
+	return ret, valid
+}