第四部分习题 - 图1第四部分习题 - 图2

    第四部分习题 - 图3

    第四部分习题 - 图4

    1. package main
    3. import (
    4.     "fmt"
    5.     "math/rand"
    6.     "time"
    7. )
    9. const (
    10.     width  = 80
    11.     height = 15
    12. )
    14. // Universe is a two-dimensional field of cells.
    15. type Universe [][]bool
    17. // NewUniverse returns an empty universe.
    18. func NewUniverse() Universe {
    19.     u := make(Universe, height)
    20.     for i := range u {
    21.         u[i] = make([]bool, width)
    22.     }
    23.     return u
    24. }
    26. // Seed random live cells into the universe.
    27. func (u Universe) Seed() {
    28.     for i := 0; i < (width * height / 4); i++ {
    29.         u.Set(rand.Intn(width), rand.Intn(height), true)
    30.     }
    31. }
    33. // Set the state of the specified cell.
    34. func (u Universe) Set(x, y int, b bool) {
    35.     u[y][x] = b
    36. }
    38. // Alive reports whether the specified cell is alive.
    39. // If the coordinates are outside of the universe, they wrap around.
    40. func (u Universe) Alive(x, y int) bool {
    41.     x = (x + width) % width
    42.     y = (y + height) % height
    43.     return u[y][x]
    44. }
    46. // Neighbors counts the adjacent cells that are alive.
    47. func (u Universe) Neighbors(x, y int) int {
    48.     n := 0
    49.     for v := -1; v <= 1; v++ {
    50.         for h := -1; h <= 1; h++ {
    51.             if !(v == 0 && h == 0) && u.Alive(x+h, y+v) {
    52.                 n++
    53.             }
    54.         }
    55.     }
    56.     return n
    57. }
    59. // Next returns the state of the specified cell at the next step.
    60. func (u Universe) Next(x, y int) bool {
    61.     n := u.Neighbors(x, y)
    62.     return n == 3 || n == 2 && u.Alive(x, y)
    63. }
    65. // String returns the universe as a string.
    66. func (u Universe) String() string {
    67.     var b byte
    68.     buf := make([]byte, 0, (width+1)*height)
    70.     for y := 0; y < height; y++ {
    71.         for x := 0; x < width; x++ {
    72.             b = ' '
    73.             if u[y][x] {
    74.                 b = '*'
    75.             }
    76.             buf = append(buf, b)
    77.         }
    78.         buf = append(buf, '\n')
    79.     }
    81.     return string(buf)
    82. }
    84. // Show clears the screen and displays the universe.
    85. func (u Universe) Show() {
    86.     fmt.Print("\x0c", u.String())
    87. }
    89. // Step updates the state of the next universe (b) from
    90. // the current universe (a).
    91. func Step(a, b Universe) {
    92.     for y := 0; y < height; y++ {
    93.         for x := 0; x < width; x++ {
    94.             b.Set(x, y, a.Next(x, y))
    95.         }
    96.     }
    97. }
    99. func main() {
    100.     a, b := NewUniverse(), NewUniverse()
    101.     a.Seed()
    103.     for i := 0; i < 300; i++ {
    104.         Step(a, b)
    105.         a.Show()
    106.         time.Sleep(time.Second / 30)
    107.         a, b = b, a // Swap universes
    108.     }
    109. }