Advent-of-Code-2023/day23/graph.go

package day23

import (
	"fmt"
	"log"
	"slices"

	mapset "github.com/deckarep/golang-set/v2"
)

type Node struct {
	index int
	c Coord
	name string
}
func (n Node)Name() string {
	var r string
	if n.index < 25 {
		num := 'A' + n.index
		r = string(rune(num))
	} else {
		num := 'a' + n.index - 25
		r = string(rune(num))
	}
	return r
}

type Graph struct {
	nodes map[Coord]Node
	nodesByIndex []Node
	edges [][]int // from, to, length. excluding from, including to
}

func MaxDist(from, to Node) (result int) {

	return
}

func PrintFieldWithGraph(g Graph, f Field) (result string) {
	result += "\n"
	for row := 0; row <= f.MaxRow; row++ {
		for col := 0; col <= f.MaxCol; col++ {
			symb := f.Cells[Coord{Row: row, Col: col}]
			if symb != Tree {
				coord := Coord{Row: row, Col: col}
				node, exists := g.nodes[coord]
				if exists {
					result += fmt.Sprint(node.Name())
				} else {
					result += "."
				}
			} else {
				result += " "
			}
		}
		result += "\n"
	}
	return
}

func CreateGraph(f Field) (g Graph) {
	startCoord := Coord{Row: 0, Col: f.StartCol}
	// directly below start
	initialPath := PathEnd{
		end: Coord{Row: 1, Col: f.StartCol}, visited: mapset.NewSet[Coord](),
	}

	g = Graph{
		nodes: map[Coord]Node{
			startCoord: Node{
				index: 0,
				c: startCoord,
				name: "A",
			},
		},
	}

	const presumedNodeCount = 36
	g.edges = make([][]int, presumedNodeCount)
	for i := 0; i < presumedNodeCount; i++ {
		g.edges[i] = make([]int, presumedNodeCount)
	}

	recursiveGraphStep(f, initialPath, &g, startCoord, 1, mapset.NewSet[Coord]())
	g.edges[0][0] = 0

	g.nodesByIndex = make([]Node, len(g.nodes))
	for _, node := range g.nodes {
		g.nodesByIndex[node.index] = node
	}

	return
}

func (g *Graph)Neighbors(node Node) (nodes []Node) {
	index := node.index
	for toIndex, len := range g.edges[index] {
		if len > 0 {
			nodes = append(nodes, g.nodesByIndex[toIndex])
		}
	}
	return
}

var maxSoFar int = -1
func CheckMaxSoFar(maybe int) {
	if maybe > maxSoFar {
		maxSoFar = maybe
	}
}

func (g *Graph) DFSLenOnGraph(atNode Node, visited mapset.Set[int],
	toNode Node, lenSoFar int) int {

	if atNode == toNode {
		CheckMaxSoFar(lenSoFar)
		return lenSoFar
	}
	log.Printf("at %+v to %+v cur dist is %d.\t\t|max so far %d| \n", atNode, toNode, lenSoFar, maxSoFar)

	neighbors := g.Neighbors(atNode)
	toVisit := slices.DeleteFunc(neighbors, func(n Node) bool {
		return visited.Contains(n.index)
	})

	if len(toVisit) == 0 {
		return -1
	}
	max := -1

	for _, nextNode := range toVisit {
		newVisited := visited.Clone()
		newVisited.Add(atNode.index)
		dist := g.edges[atNode.index][nextNode.index]
		maxFromNext := g.DFSLenOnGraph(nextNode, newVisited, toNode, lenSoFar + dist)
		if maxFromNext > max {
			max = maxFromNext
		}
	}

	return max
}

// run dfs, remembering from which remembers from which node we go, which path already traversed
func recursiveGraphStep(f Field, p PathEnd, g *Graph, goingFrom Coord, goingLen int, visitedPathPoints mapset.Set[Coord]) {
	// log.Printf("entering coord %+v. from %+v with len %d\n", p.end, goingFrom, goingLen)

	// if visitedPathPoints.Contains(p.end) {
	// 	return
	// }

	neighbors := f.NeighborsPart2(p.end)

	isCrossRoad := len(neighbors) > 2
	if isCrossRoad {
		log.Println("this should be crossroad ", p.end)
	}
	isStart := p.end == Coord{Row: 0, Col: f.StartCol}
	isEnd := p.end == f.EndCoord()
	if isEnd {
		log.Println("this should be end ", p.end)
	}

	isNode := isCrossRoad || isStart || isEnd

	continuedPaths := ExtendPath(p, f)

	if !isNode {
		// just recurse into next paths, from same node, with increased len
		visitedPathPoints.Add(p.end)
		for _, nextStep := range continuedPaths {
			recursiveGraphStep(f, nextStep, g, goingFrom, goingLen+1, visitedPathPoints)
		}
	} else {
		node, known := g.nodes[p.end]
		// check if known, if not known - create
		if !known {
			node = Node{
				c: p.end,
				index: len(g.nodes),
			}
			node.name = node.Name()
			g.nodes[p.end] = node
			log.Printf("creating node %s %+v\n", node.Name(), node)
		}
		from := g.nodes[goingFrom]
		log.Printf("from %s to %s\n", from.Name(), node.Name())
		// and add vertices to currently traversed
		if g.edges[node.index][from.index] == 0 {
			g.edges[node.index][from.index] = goingLen
			g.edges[from.index][node.index] = goingLen
		} else {
			knownEdge := g.edges[node.index][from.index]
			if goingLen > knownEdge {
				g.edges[node.index][from.index] = goingLen
				g.edges[from.index][node.index] = goingLen
			}
		}
		// NOTE ah, it's possible to have two edges between i and j
		// but, i only need the longest one
		// log.Printf("adding edges between %d & %d of len %d\n", node.index, from.index, goingLen)

		// continue with new 'from' and len of 1
		if !known {
			for _, nextStep := range continuedPaths {
				log.Printf("from %s should recurse to %+v", node.Name(), nextStep)
				recursiveGraphStep(f, nextStep, g, p.end, 1, visitedPathPoints)
			}
		}
	}

	return
}

func GraphToMermaid(g Graph) (result string) {
	result += "\nflowchart LR\n"
	lines := mapset.NewSet[string]()
	for _, node := range g.nodes {
		for to, len := range g.edges[node.index] {
			var toNode Node
			for _, other := range g.nodes {
				if other.index == to {
					toNode = other
				}
			}
			if len > 0 {
				var fromName, toName string
				if node.index < toNode.index {
					fromName = node.Name()
					toName = toNode.Name()
				} else {
					fromName = toNode.Name()
					toName = node.Name()
				}
				line := fmt.Sprintf("\t%s---|length %d|%s\n", fromName, len, toName)
				lines.Add(line)
			}
		}
		// result += fmt.Sprintf("%s--|%d|%s\n", a ...any)
	}

	for line := range lines.Iter() {
		result += line
	}

	return
}