golang實現障礙、轉彎最少的A*尋路

目錄

• 目標：
• 要點：
• 源碼：

目標：

• 優先尋找無障礙的路徑
• 目標不可達時，尋找障礙最少的路徑
• 路徑長度相等時，優先轉彎最少的路徑
• 多個目標點時，根據以上要求到達其中一個目標點便可

要點：

• 最優格子的選取，先對open list排序，而後從open list中出隊

源碼：

package main

import (
    "errors"
    "fmt"
    "math"
    "sort"
)

type Node struct {
    Parent *Node
    Pos    []int32
    GDir   []int32
    G      float32
    H      float32
    F      float32
    B      int // 障礙Block
    T      int // 轉彎turn
}

func (node *Node) String() string {
    return fmt.Sprintf("%#v", node)
}

// 優先障礙最少，其次路徑最短，再次轉彎最少
func (best *Node) IsBetterThan(node *Node) bool {
    if best.B < node.B {
        return true
    }
    if best.B > node.B {
        return false
    }
    if best.F < node.F {
        return true
    }
    if best.F > node.F {
        return false
    }
    if best.T < node.T {
        return true
    }
    if best.T > node.T {
        return false
    }
    return false
}

type NodeList []*Node

func (nl NodeList) Len() int      { return len(nl) }
func (nl NodeList) Swap(i, j int) { nl[i], nl[j] = nl[j], nl[i] }
func (nl NodeList) Less(i, j int) bool {
    best, node := nl[i], nl[j]
    return best.IsBetterThan(node)
}

func (nl NodeList) String() string {
    s := "*******NodeList********\n"
    for i, node := range nl {
        s = fmt.Sprintf("%s%d = %s\n", s, i, node.String())
    }
    return s
}

func (nl NodeList) NodeIdx(node *Node) int {
    for i, n := range nl {
        if n.Pos[0] == node.Pos[0] && n.Pos[1] == node.Pos[1] {
            return i
        }
    }
    return -1
}

type AStar struct {
    W        int32
    H        int32
    SPos     []int32
    EPos     []int32
    Open     NodeList // 使用list，起點，終點相同時每次的路徑都同樣，換成map時，每次的路徑可能不同。
    CloseMap map[int32]struct{}
}

const (
    NODE_OPEN    int32 = iota // 可通行
    NODE_BARRIER              // 障礙，沒法到達目的地時，返回障礙最少的路徑
    NODE_NO_PASS              // 不可通行，邊界等不能通行
)

func (a *AStar) newNode(parent *Node, x, y int32, dir []int32) *Node {
    state := a.GetNodeState(x, y)
    if state != NODE_OPEN && state != NODE_BARRIER {
        a.addClose(&Node{Pos: []int32{x, y}})
        return nil
    }
    b, t := 0, 0
    if parent != nil {
        b = parent.B
        if dir[0] == parent.GDir[0] && dir[1] == parent.GDir[1] {
            t = parent.T
        } else {
            t = parent.T + 1
        }
    }
    if state == NODE_BARRIER {
        b++
    }
    pos := []int32{x, y}
    g := a.getG(pos, parent)
    h := a.getH(pos, a.EPos)
    return &Node{
        Parent: parent,
        Pos:    pos,
        G:      g,
        H:      h,
        F:      g + h,
        B:      b,
        T:      t,
        GDir:   dir,
    }
}

func (a *AStar) GetNodeState(x, y int32) int32 {
    if x < 0 || x >= a.W || y < 0 || y >= a.H {
        return NODE_NO_PASS
    }
    //fmt.Println("GetNodeState", x, y, GMap[x][y])
    return GMap[x][y]
}

// 計算g值；直走=1；斜走=1.4
func (a *AStar) getG(pos1 []int32, parent *Node) float32 {
    if parent == nil {
        return 0
    }
    pos2 := parent.Pos
    g := parent.G
    if pos1[0] == pos2[0] {
        return g + float32(math.Abs(float64(pos1[1]-pos2[1])))
    } else if pos1[1] == pos2[1] {
        return g + float32(math.Abs(float64(pos1[0]-pos2[0])))
    } else {
        return g + float32(math.Abs(float64(pos1[0]-pos2[0])*1.4))
    }
}

// 計算h值
func (a *AStar) getH(pos1, pos2 []int32) float32 {
    return float32(math.Abs(float64(pos1[0]-pos2[0])) + math.Abs(float64(pos1[1]-pos2[1])))
}

func (a *AStar) addOpen(node *Node) {
    //idx := a.getNodeIdxInOpen(node)
    idx := a.Open.NodeIdx(node)
    //fmt.Println(a.Open)
    //fmt.Println("addOpen:", idx, "node:", node, "patrnt ", node.Parent)
    if idx >= 0 {
        n := a.Open[idx]
        if node.IsBetterThan(n) {
            a.Open[idx] = node
        }
    } else {
        a.Open = append(a.Open, node)
    }
}

// x, y 對應的node在open中的idx
func (a *AStar) getNodeIdxInOpen(node *Node) int {
    x, y := node.Pos[0], node.Pos[1]
    l := len(a.Open)
    if l == 0 {
        return -1
    }
    idx := sort.Search(len(a.Open),
        func(i int) bool {
            pos := a.Open[i].Pos
            return pos[0] == x && pos[1] == y
        })
    // sort.Search 對已排序的list使用二分查找，
    // sort.Search 的坑，未找到返回的值等於list長度
    if idx == l {
        return -1
    }
    return idx
}

// 從open中出棧，即最優的格子
func (a *AStar) getMinNode() *Node {
    sort.Sort(a.Open)
    node := a.Open[0]
    a.Open = a.Open[1:]
    return node
}

// 添加到close中,
func (a *AStar) addClose(n *Node) {
    x, y := n.Pos[0], n.Pos[1]
    key := x*a.W*10 + y
    a.CloseMap[key] = struct{}{}
}

// 判斷是否在close中
func (a *AStar) isInClose(x, y int32) (ok bool) {
    key := x*a.W*10 + y
    _, ok = a.CloseMap[key]
    return
}

// 拓展周邊方向的node
func (a *AStar) extendNeighbours(c *Node) {
    for _, dir := range GDir {
        x := c.Pos[0] + dir[0]
        y := c.Pos[1] + dir[1]
        if a.isInClose(x, y) {
            continue
        }
        node := a.newNode(c, x, y, dir)
        if node == nil {
            continue
        }
        a.addOpen(node)
    }
}

func (a *AStar) isTarget(n *Node, ePos []int32) bool {
    if n == nil {
        return false
    }
    if n.Pos[0] == ePos[0] && n.Pos[1] == ePos[1] {
        return true
    }
    return false
}

// 從結束點回溯到開始點，開始點的parent == None
func (a *AStar) makePath(p *Node) [][]int32 {
    path := make([][]int32, 0)
    for p != nil {
        path = append([][]int32{p.Pos}, path[:]...)
        p = p.Parent
    }
    fmt.Println("********makePath:", path)
    return path
}

// 路徑查找主函數
func (a *AStar) findPath(sPos, ePos []int32) (path [][]int32, block, turn int, err error) {
    state := a.GetNodeState(sPos[0], sPos[1])
    if state != NODE_OPEN && state != NODE_BARRIER {
        err = errors.New(fmt.Sprintf("spos state is %d", state))
        return
    }

    estate := a.GetNodeState(ePos[0], ePos[1])
    if estate != NODE_OPEN && estate != NODE_BARRIER {
        err = errors.New(fmt.Sprintf("ePos state is %d", estate))
        return
    }

    a.SPos, a.EPos = sPos, ePos
    // 構建開始節點
    s := a.newNode(nil, sPos[0], sPos[1], []int32{0, 0})
    a.addOpen(s)
    for {
        if len(a.Open) <= 0 {
            err = errors.New("not find Open list is nil")
            return
        }
        p := a.getMinNode()
        //fmt.Println(fmt.Sprintf("---min p = %#v", p))
        if a.isTarget(p, ePos) {
            path = a.makePath(p)
            block, turn = p.B, p.T
            return
        }
        a.extendNeighbours(p)
        a.addClose(p)
    }
    return
}

// 查詢過的全部格子
func (a *AStar) getSearched() []int32 {
    l := make([]int32, 0)
    for _, i := range a.Open {
        if i != nil {
            l = append(l, i.Pos[0], i.Pos[1])
        }
    }
    for k, _ := range a.CloseMap {
        x := k / a.W * 10
        y := k % a.W * 10
        l = append(l, x, y)
    }
    return l
}

// 清空open和close
func (a *AStar) clean() {
    a.Open = make(NodeList, 0)
    a.CloseMap = make(map[int32]struct{})
}

func NewAstar() *AStar {
    a := &AStar{
        W:        int32(len(GMap)),
        H:        int32(len(GMap[0])),
        Open:     make(NodeList, 0),
        CloseMap: make(map[int32]struct{}),
    }
    fmt.Println("NewAstar", a.W, a.H)
    return a
}

// 終點不惟一時找到最優的路徑
func FindPathIgnoreBlock(sPos []int32, ePos [][]int32) {
    a := NewAstar()
    if a == nil {
        return
    }
    var path [][]int32
    var block, turn int
    for _, e := range ePos {
        a.clean()
        p, b, t, err := a.findPath(sPos, e)
        fmt.Println("FindPathIgnoreBlock:",
            fmt.Sprint("sPos", sPos),
            fmt.Sprint("ePos", e),
            fmt.Sprint("path", p),
            fmt.Sprint("Block", b),
            fmt.Sprint("turn", t),
            fmt.Sprint("err", err))
        if err != nil {
            continue
        }
        if path == nil {
            path, block, turn = p, b, t
            continue
        }
        stepNum, newStep := len(path), len(p)
        fmt.Println("stepNum", stepNum, "newStep", newStep)
        if stepNum < newStep {
            continue
        }
        if stepNum > newStep {
            path, block, turn = p, b, t
            continue
        }
        if block < b {
            continue
        }
        if block > b {
            path, block, turn = p, b, t
            continue
        }

        if turn < t {
            continue
        }

        if turn > b {
            path, block, turn = p, b, t
            continue
        }
    }
    fmt.Println("********end, FindPathIgnoreBlock", path, block, turn)
}

var (
    GDir [][]int32 //方向
    GMap [][]int32 //地圖
)

func init() {
    GDir = [][]int32{{1, 0}, {0, 1}, {0, -1}, {-1, 0}}
    GMap = [][]int32{
        {0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {2, 2, 2, 2, 2, 1, 2, 2, 1, 2, 2, 2, 2, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 2, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 2, 1, 0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
        {0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0},
    }
    fmt.Println("----init:", len(GMap[0]), len(GMap), NODE_OPEN, NODE_BARRIER, NODE_NO_PASS)
}

func main() {
    FindPathIgnoreBlock([]int32{3, 2}, [][]int32{{5, 3}})
}