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Add 07: Magic square solver
Initial dumb implementation. - CPU profiling. To see the result, run 07-magic_square, execute `go tool pprof 07-magic_square path/to/cpu.pprof` and input `top[Enter]` in the prompt. - Generic algorithm. The trick is the Float64Slice adaptor; see [1]. Maybe I will use the technique used in the sort library[2][3] which allows simpler API. [1]: http://stackoverflow.com/a/6256127/5266681 [2]: golang/go#16721 [3]: golang/go@22a2bdf
1 parent d9860d4 commit 57ec35f

11 files changed

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‎07-magic_square/main.go

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package main
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import (
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"fmt"
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"math/rand"
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"os"
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"time"
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"github.com/frickiericker/learn-go/07-magic_square/matrix"
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"github.com/pkg/profile"
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)
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func main() {
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if err := run(); err != nil {
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fmt.Fprintf(os.Stderr, "error: %s\n", err)
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os.Exit(1)
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}
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}
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func run() error {
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defer profile.Start(profile.CPUProfile).Stop()
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n := 5
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rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
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solver := NewMagicSquareSolver(n, rnd)
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solver.Randomize()
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for {
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if solver.SearchNeighbor() == 0 {
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break
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}
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}
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matrix.Print(solver.Get())
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return nil
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}

‎07-magic_square/matrix/interface.go

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package matrix
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type Interface interface {
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Rows() int
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Cols() int
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Get(i, j int) float64
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Set(i, j int, value float64)
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}

‎07-magic_square/matrix/io.go

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package matrix
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import (
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"fmt"
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)
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func Print(mat Interface) {
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for i := 0; i < mat.Rows(); i++ {
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for j := 0; j < mat.Cols(); j++ {
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if j > 0 {
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fmt.Print("\t")
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}
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fmt.Printf("%.3g", mat.Get(i, j))
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}
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fmt.Print("\n")
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}
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}

‎07-magic_square/matrix/square.go

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package matrix
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type Square struct {
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data []float64
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size int
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}
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func NewSquare(size int) *Square {
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return &Square{
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data: make([]float64, size*size),
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size: size,
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}
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}
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func (mat *Square) Data() []float64 {
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return mat.data
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}
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func (mat *Square) Size() int {
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return mat.size
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}
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func (mat *Square) Rows() int {
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return mat.size
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}
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func (mat *Square) Cols() int {
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return mat.size
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}
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func (mat *Square) locate(i, j int) int {
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return i*mat.size + j
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}
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func (mat *Square) Get(i, j int) float64 {
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return mat.data[mat.locate(i, j)]
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}
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func (mat *Square) Set(i, j int, value float64) {
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mat.data[mat.locate(i, j)] = value
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}

‎07-magic_square/matrix/square_test.go

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package matrix
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import (
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"testing"
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)
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func TestNewSquare_checkSize(t *testing.T) {
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sq := NewSquare(7)
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if result := sq.Size(); result != 7 {
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t.Errorf("unexpected result from Size() %v", result)
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}
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if result := sq.Rows(); result != 7 {
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t.Errorf("unexpected result from Rows() %v", result)
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}
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if result := sq.Cols(); result != 7 {
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t.Errorf("unexpected result from Cols() %v", result)
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}
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if result := sq.Data(); len(result) != 7*7 {
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t.Errorf("unexpected result from Data() %v", result)
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}
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}
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func TestSquare_Get_safeRange(t *testing.T) {
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sq := NewSquare(5)
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for i := 0; i < 5; i++ {
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for j := 0; j < 5; j++ {
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sq.Get(i, j)
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}
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}
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}
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func TestSquare_Set_safeRange(t *testing.T) {
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sq := NewSquare(5)
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for i := 0; i < 5; i++ {
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for j := 0; j < 5; j++ {
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sq.Set(i, j, 1.23)
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}
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}
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}

‎07-magic_square/seq/interface.go

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package seq
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type Interface interface {
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Len() int
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}
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type Swappable interface {
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Interface
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Swap(i, j int)
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}

‎07-magic_square/seq/shuffle.go

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package seq
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import (
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"math/rand"
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)
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func Shuffle(seq Swappable, rnd *rand.Rand) {
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for i := seq.Len() - 1; i > 0; i-- {
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j := rnd.Intn(i + 1)
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seq.Swap(i, j)
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}
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}

‎07-magic_square/seq/shuffle_test.go

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package seq
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import (
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"math/rand"
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"testing"
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)
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func TestShuffle_isPermutation(t *testing.T) {
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rnd := rand.New(rand.NewSource(0))
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seq := Float64Slice{[]float64{1, 2, 3, 4}}
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Shuffle(seq, rnd)
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counter := map[float64]int{}
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for _, value := range seq.slice {
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counter[value] += 1
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}
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for _, count := range counter {
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if count != 1 {
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t.Errorf("%v", seq)
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}
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}
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}
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func TestShuffle_allowEmptySeq(t *testing.T) {
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rnd := rand.New(rand.NewSource(0))
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seq := Float64Slice{[]float64{}}
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Shuffle(seq, rnd)
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}

‎07-magic_square/seq/slice.go

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package seq
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type Float64Slice struct {
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slice []float64
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}
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func NewFloat64Slice(slice []float64) Float64Slice {
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return Float64Slice{slice}
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}
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func (seq Float64Slice) Len() int {
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return len(seq.slice)
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}
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func (seq Float64Slice) Swap(i, j int) {
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seq.slice[i], seq.slice[j] = seq.slice[j], seq.slice[i]
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}

‎07-magic_square/seq/slice_test.go

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package seq
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import (
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"reflect"
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"testing"
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)
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func TestFloat64Slice_Len(t *testing.T) {
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seq := Float64Slice{[]float64{1, 2, 3, 4}}
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if seq.Len() != 4 {
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t.Errorf("%v", seq)
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}
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}
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func TestFloat64Slice_Swap(t *testing.T) {
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seq := Float64Slice{[]float64{1, 2, 3, 4}}
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seq.Swap(1, 2)
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if !reflect.DeepEqual(seq.slice, []float64{1, 3, 2, 4}) {
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t.Errorf("%v", seq)
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}
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}

‎07-magic_square/solver.go

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package main
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import (
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"math"
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"math/rand"
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"github.com/frickiericker/learn-go/07-magic_square/matrix"
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"github.com/frickiericker/learn-go/07-magic_square/seq"
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)
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type MagicSquareSolver struct {
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square *matrix.Square
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magic float64
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rnd *rand.Rand
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}
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func NewMagicSquareSolver(size int, rnd *rand.Rand) *MagicSquareSolver {
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square := matrix.NewSquare(size)
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for i := range square.Data() {
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square.Data()[i] = float64(i + 1)
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}
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return &MagicSquareSolver{
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square: square,
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magic: float64(magicConstant(size)),
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rnd: rnd,
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}
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}
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func (solver *MagicSquareSolver) Get() *matrix.Square {
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return solver.square
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}
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func (solver *MagicSquareSolver) Randomize() {
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seq.Shuffle(seq.NewFloat64Slice(solver.square.Data()), solver.rnd)
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}
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func (solver *MagicSquareSolver) evaluate() float64 {
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loss := float64(0)
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magic := solver.magic
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for i := 0; i < solver.square.Size(); i++ {
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loss += math.Abs(sumRow(solver.square, i) - magic)
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loss += math.Abs(sumCol(solver.square, i) - magic)
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}
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loss += math.Abs(sumDiag(solver.square) - magic)
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loss += math.Abs(sumAntidiag(solver.square) - magic)
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return loss
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}
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func (solver *MagicSquareSolver) SearchNeighbor() float64 {
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n := solver.square.Size()
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data := solver.square.Data()
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c1 := solver.rnd.Intn(n * n)
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c2 := solver.rnd.Intn(n * n)
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lossBefore := solver.evaluate()
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data[c1], data[c2] = data[c2], data[c1]
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lossAfter := solver.evaluate()
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if lossAfter - 3 > lossBefore {
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data[c1], data[c2] = data[c2], data[c1]
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return lossBefore
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}
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return lossAfter
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}
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func sumRow(square *matrix.Square, row int) float64 {
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sum := float64(0)
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for col := 0; col < square.Cols(); col++ {
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sum += square.Get(row, col)
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}
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return sum
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}
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func sumCol(square *matrix.Square, col int) float64 {
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sum := float64(0)
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for row := 0; row < square.Rows(); row++ {
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sum += square.Get(row, col)
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}
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return sum
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}
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func sumDiag(square *matrix.Square) float64 {
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sum := float64(0)
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for i := 0; i < square.Size(); i++ {
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sum += square.Get(i, i)
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}
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return sum
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}
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func sumAntidiag(square *matrix.Square) float64 {
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sum := float64(0)
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size := square.Size()
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for i := 0; i < size; i++ {
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sum += square.Get(i, size-i-1)
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}
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return sum
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}
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func magicConstant(n int) int {
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return n * (n*n + 1) / 2
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}

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