Problem 228 at project Euler. Find length of S_1864 + ... + S_1909, where S_[number] is [number]-sided polygon. http://projecteuler.net/problem=228

minkowsky.go

package main

import (
  "math"
  "fmt"
)

type Vertex struct {
  x float64
  y float64
}

type Shape []Vertex

const RADIAN_TO_DEGREE = 180 / math.Pi

// Create shape with given size. Shape is array of Vertices.
//
func CreateShape(size int) []Vertex {
  result := make([]Vertex, size)
  for i := 0; i < size; i++ {
    angle := RADIAN_TO_DEGREE * float64(2 * (i + 1) * 180) / float64(size)
    result[i] = Vertex { math.Cos(angle), math.Sin(angle) }
  }
  return result
}

// Check if array has given value.
//
func (shape Shape) HasValue(value Vertex) bool {
  for _, v := range shape {
    if v == value { return true }
  }
  return false
}

// Find new shape as sum of two given.
//
func Sum(a, b []Vertex) []Vertex {
  result := make([]Vertex, len(a) * len(b))
  columnSize := len(a)
  for aIndex, aValue := range a {
    for bIndex, bValue := range b {
      x := aValue.x + bValue.x
      y := aValue.y + bValue.y
      result[aIndex * columnSize + bIndex] = Vertex { x, y }
    }
  }
  return Shape(result).Uniq()
}

// Uniq given array.
//
func (shape Shape) Uniq() Shape {
  result := make([]Vertex, 0)
  for _, value := range shape {
    if !Shape(result).HasValue(value) { result = append(result, value) }
  }
  return result
}

func main() {
  left, right := 1864, 1909
  result := CreateShape(left)
  for left < right {
    left += 1
    shape := CreateShape(left)
    result = append(result, shape...)
  }
  fmt.Println(len(Shape(result).Uniq()))
}