79 lines
1.5 KiB
Go
79 lines
1.5 KiB
Go
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package main
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import (
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"cmp"
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pq "github.com/emirpasic/gods/v2/queues/priorityqueue"
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)
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type Position struct {
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y, x int
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}
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func (p *Position) add(v Position) Position {
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return Position{
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y: p.y + v.y,
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x: p.x + v.x,
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}
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}
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type QueueEntry struct {
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time int
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pos Position
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}
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func byTime(a, b QueueEntry) int {
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return cmp.Compare(a.time, b.time)
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}
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func minimumTime(grid [][]int) int {
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if grid[0][1] > 1 && grid[1][0] > 1 {
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return -1
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}
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DIRECTIONS := []Position{
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Position{1, 0}, Position{-1, 0}, Position{0, 1}, Position{0, -1},
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}
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rows, cols := len(grid), len(grid[0])
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visited := make([][]bool, rows)
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for i, _ := range visited {
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visited[i] = make([]bool, cols)
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}
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valid := func(pos Position) bool {
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return pos.y >= 0 && pos.y < len(visited) &&
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pos.x >= 0 && pos.x < len(visited[pos.y]) &&
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!visited[pos.y][pos.x]
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}
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q := pq.NewWith[QueueEntry](byTime)
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q.Enqueue(QueueEntry{grid[0][0], Position{0, 0}})
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for current, ok := q.Dequeue(); ok; current, ok = q.Dequeue() {
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if current.pos.y == rows-1 && current.pos.x == cols-1 {
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return current.time
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}
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if visited[current.pos.y][current.pos.x] {
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continue
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}
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visited[current.pos.y][current.pos.x] = true
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for _, dir := range DIRECTIONS {
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next := current.pos.add(dir)
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if !valid(next) {
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continue
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}
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waiting := 0
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if (grid[next.y][next.x]-current.time)%2 == 0 {
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waiting = 1
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}
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q.Enqueue(QueueEntry{pos: next, time: max(grid[next.y][next.x]+waiting, current.time+1)})
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}
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}
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return -1
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}
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