114 lines
2.2 KiB
Go
114 lines
2.2 KiB
Go
package main
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import (
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"fmt"
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h "git.bullercodeworks.com/brian/adventofcode/helpers"
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)
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func main() {
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inp := h.StdinToStringSlice()
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// size, bytes := 6, 12 // Test Input
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size, bytes := 70, 1024 // Actual Input
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part1(inp, size, bytes)
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fmt.Println()
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part2(inp, size, bytes)
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}
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func part1(inp []string, size, bytes int) {
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// bytes:= 12 // Test Input
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m := h.NewCoordByteMap()
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m.BRX, m.BRY = size, size
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drops := parseInput(inp)
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for i := 0; i < bytes; i++ {
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m.Put(drops[i], '#')
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}
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fmt.Println("# Part 1")
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fmt.Println(FindShortestPath(m, func(a, b State) bool {
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return a.cnt+a.dist < b.cnt+b.dist
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}))
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}
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func part2(inp []string, size, bytes int) {
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m := h.NewCoordByteMap()
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m.BRX, m.BRY = size, size
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drops := parseInput(inp)
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// We can skip up to 'bytes', part1 showed that that many work
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for i := 0; i < bytes; i++ {
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m.Put(drops[i], '#')
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}
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fmt.Println("# Part 2")
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for tm, b := range drops[bytes+1:] {
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m.Put(b, '#')
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if FindShortestPath(m, func(a, b State) bool {
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return a.dist < b.dist
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}) == -1 {
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fmt.Printf("Blocked at %d: %s\n", bytes+tm, b.String())
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return
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}
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}
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}
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func parseInput(inp []string) []h.Coordinate {
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var ret []h.Coordinate
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for i := range inp {
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c := h.Coordinate{}
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fmt.Sscanf(inp[i], "%d,%d", &c.X, &c.Y)
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ret = append(ret, c)
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}
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return ret
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}
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type State struct {
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c h.Coordinate
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cnt int
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dist int
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}
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func FindShortestPath(inp h.CoordByteMap, less func(a, b State) bool) int {
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visited := make(map[h.Coordinate]State)
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end := h.Coordinate{X: inp.BRX, Y: inp.BRY}
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start := h.Coordinate{X: 0, Y: 0}
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startState := State{
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c: start,
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cnt: 0,
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dist: start.Distance(end),
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}
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queue := h.NewHeap[State](less)
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queue.Push(startState)
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for queue.Len() > 0 {
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step := queue.Pop()
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if step.c.Equals(end) {
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visited[end] = step
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break
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}
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if _, ok := visited[step.c]; ok {
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continue
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}
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visited[step.c] = step
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// Find next steps
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for _, n := range step.c.GetOrthNeighbors() {
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if !inp.ContainsCoord(n) || inp.Get(n) == '#' {
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continue
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}
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if _, ok := visited[n]; ok {
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continue
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}
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nState := State{
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c: n,
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cnt: step.cnt + 1,
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dist: n.Distance(end),
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}
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queue.Push(nState)
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}
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}
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if v, ok := visited[end]; ok {
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return v.cnt
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}
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return -1
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}
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