100 lines
1.8 KiB
Go
100 lines
1.8 KiB
Go
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package main
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import (
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"bufio"
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"container/heap"
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"fmt"
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"os"
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)
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type Node struct {
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x, y, cost int
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index int
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}
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type NodeQueue []*Node
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func (pq NodeQueue) Len() int { return len(pq) }
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func (pq NodeQueue) Less(i, j int) bool { return pq[i].cost < pq[j].cost }
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func (pq NodeQueue) Swap(i, j int) {
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pq[i], pq[j] = pq[j], pq[i]
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pq[i].index = i
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pq[j].index = j
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}
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func (pq *NodeQueue) Push(x interface{}) {
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item := x.(*Node)
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item.index = len(*pq)
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*pq = append(*pq, item)
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}
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func (pq *NodeQueue) Pop() interface{} {
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p := *pq
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l := len(p) - 1
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item := p[l]
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p[l] = nil
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*pq = p[0:l]
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return item
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}
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func (pq *NodeQueue) Update(n *Node, cost int) {
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n.cost = cost
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heap.Fix(pq, n.index)
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}
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var (
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grid [][]byte
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costs [][]Node
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nq = make(NodeQueue, 1)
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size int
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)
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func calculateTentativeDistance(x, y, cost int) {
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if x < 0 || x >= size || y < 0 || y >= size {
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return
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}
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cost += int(grid[y][x])
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if costs[y][x].cost == 0 {
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costs[y][x].cost = cost
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heap.Push(&nq, &costs[y][x])
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} else if cost < costs[y][x].cost {
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nq.Update(&costs[y][x], cost)
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}
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}
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func main() {
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scanner := bufio.NewScanner(os.Stdin)
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scanner.Scan()
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line := scanner.Text()
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size = len(line)
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y := 0
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for {
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l := make([]byte, size)
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for i := 0; i < size; i++ {
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l[i] = line[i] - '0'
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}
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grid = append(grid, l)
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c := make([]Node, size)
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for j := 0; j < size; j++ {
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c[j] = Node{x: j, y: y}
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}
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costs = append(costs, c)
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if !scanner.Scan() {
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break
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}
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line = scanner.Text()
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y++
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}
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grid[0][0] = 0
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nq[0] = &costs[0][0]
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heap.Init(&nq)
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for {
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n := heap.Pop(&nq).(*Node)
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if n.x == size-1 && n.y == size-1 {
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fmt.Println(n.cost)
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break
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}
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calculateTentativeDistance(n.x-1, n.y, n.cost)
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calculateTentativeDistance(n.x+1, n.y, n.cost)
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calculateTentativeDistance(n.x, n.y-1, n.cost)
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calculateTentativeDistance(n.x, n.y+1, n.cost)
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}
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}
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