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MilyMilo/ulam.go

Created March 29, 2018 16:30
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  1. MilyMilo created this gist Mar 29, 2018.
    119 changes: 119 additions & 0 deletions ulam.go
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,119 @@
    package main

    import (
    "fmt"
    "math"
    "strings"
    )

    const (
    RIGHT = iota
    UP
    LEFT
    DOWN
    )

    func generate(size, max int) {
    matrix := make([][]string, size)

    for i := 0; i < size; i++ {
    matrix[i] = make([]string, size)
    }

    dir := RIGHT
    y := size / 2
    var x int

    if size%2 == 0 {
    x = y - 1
    } else {
    x = y
    }

    for j := 1; j <= size*size; j++ {
    if j > max {
    matrix[y][x] = " "
    } else if isPrime(j) {
    matrix[y][x] = "#"
    } else {
    matrix[y][x] = "."
    }

    switch dir {
    case RIGHT:
    if x <= size-1 && matrix[y-1][x] == "" && j > 1 {
    dir = UP
    }
    case UP:
    if matrix[y][x-1] == "" {
    dir = LEFT
    }
    case LEFT:
    if x == 0 || matrix[y+1][x] == "" {
    dir = DOWN
    }
    case DOWN:
    if matrix[y][x+1] == "" {
    dir = RIGHT
    }
    }

    switch dir {
    case RIGHT:
    x += 1
    case UP:
    y -= 1
    case LEFT:
    x -= 1
    case DOWN:
    y += 1
    }
    }

    for _, row := range matrix {
    out := strings.Join(row, "")
    out = strings.Replace(out, " ", "o", -1)
    if !strings.ContainsAny(out, "# .") {
    continue
    }
    out = strings.TrimRight(out, "o")
    out = strings.Replace(out, "o", " ", -1)
    fmt.Println(out)
    }
    }

    func isPrime(a int) bool {
    if a == 2 {
    return true
    }
    if a <= 1 || a%2 == 0 {
    return false
    }
    max := int(math.Sqrt(float64(a)))
    for n := 3; n <= max; n += 2 {
    if a%n == 0 {
    return false
    }
    }
    return true
    }

    func getSize(max int) float64 {
    for {
    sqrt := math.Sqrt(float64(max))
    if sqrt*sqrt == float64(int(sqrt)*int(sqrt)) {
    return math.Sqrt(float64(max))
    }
    max++
    }
    }

    func main() {
    var input int
    fmt.Scanf("%d", &input)
    if input != 1 {
    generate(int(getSize(input)), input)
    } else {
    fmt.Println(".")
    }
    }