go-广度优先算法

1.迷宫

6 5
0 1 0 0 0
0 0 0 1 0
0 1 0 1 0
1 1 1 0 0
0 1 0 0 1
0 1 0 0 0

2.思路

• 用循环创建二维slice
• 使用slice来实现队列
• 用Fscanf读取文件
• 对Point进行抽象

3.代码

package main

import (
    "fmt"
    "os"
)

//读取迷宫数据,放入二维数组中
func readMaze(filename string) [][]int {
    file, err := os.Open(filename)
    if err != nil {
        panic("文件不存在")
    }
    defer file.Close()

    var row, col int

    fmt.Fscanf(file, "%d %d", &row, &col)

    maze := make([][]int, row)

    for i := range maze {
        maze[i] = make([]int, col)
        for j := range maze[i] {
            fmt.Fscanf(file, "%d", &maze[i][j])
        }
    }

    return maze
}

type point struct {
    i, j int
}

//当前点的上,左边,下,右,
var dirs = [4]point{
    {-1, 0}, {0, -1}, {1, 0}, {0, 1},
}

//当前点,移动
func (p point) add(r point) point {
    return point{p.i + r.i, p.j + r.j}
}

//取出当前点对应的值
func (p point) at(grid [][]int) (int, bool) {
    if p.i < 0 || p.i >= len(grid) {
        return 0, false
    }

    if p.j < 0 || p.j >= len(grid[0]) {
        return 0, false
    }

    return grid[p.i][p.j], true
}

//遍历迷宫
func walk(maze [][]int, start, end point) ([][]int) {
    steps := make([][]int, len(maze))

    for i := range steps {
        steps[i] = make([]int, len(maze[0]))
    }

    //队列,存放将要探索的点
    Q := []point{start}

    for len(Q) > 0 {
        cur := Q[0]
        Q = Q[1:]

        //到终点了
        if cur == end {
            break
        }

        for _, dir := range dirs {
            next := cur.add(dir)

            //next 在maze 中的值为0才可以
            val, ok := next.at(maze)
            if !ok || val == 1 {
                //没有值,或者撞墙,
                continue
            }

            val, ok = next.at(steps)
            if !ok || val != 0 {
                //探索过的位置,不再进行探索
                continue
            }

            //回到原点,不进行探索
            if next == start {
                continue
            }

            curSteps, _ := cur.at(steps)

            steps[next.i][next.j] = curSteps + 1
            Q = append(Q, next)
        }

    }

    return steps
}

func main() {
    maze := readMaze("maze/maze.in")

    steps := walk(maze, point{0, 0}, point{len(maze) - 1, len(maze[0]) - 1})

    for _, row := range steps {
        for _, val := range row {
            fmt.Printf("%3d ", val)
        }
        fmt.Print("\n")
    }
}