Go言語で数独（ナンプレ）を解くコードを書いてみた

package main

import (
  "flag"
  "fmt"
  "strconv"
  "strings"
)

type Result struct {
  N         int
  X         int
  Y         int
  Ok        bool
  Value     int
  Candidate []int
  Empty     int
  Field     [][]int
}

func main() {
  const size = 9
  const maxTry = 1000
  flag.Parse()
  numStr := flag.Arg(0)
  field := load(numStr, size)

  fmt.Println("")
  fmt.Println("[START]")
  empty := counting(field, size)
  result := Result{Field: field}
  printResult(result, size, false)
  n := 0
  for empty > 0 || n < maxTry {
    for i := 0; i < size; i++ {
      for j := 0; j < size; j++ {
        n++
        cursorValue := field[i][j]
        if cursorValue == 0 {
          candidate := buildCandidate(size)
          value, ok, filteredCandidate := filter(field, j, i, size, candidate)
          if ok {
            field[i][j] = value
            empty--
          }
          result = Result{N: n, X: j, Y: i, Ok: ok, Value: value, Candidate: filteredCandidate, Empty: empty, Field: field}
          printResult(result, size, true)
        }
      }
    }
  }

  if empty == 0 {
    fmt.Println("[END]")
  } else {
    fmt.Println("[FAILED]")
  }
  printResult(result, size, false)

}

func load(numStr string, size int) [][]int {
  field := [][]int{}
  for i := 0; i < size; i++ {
    start := i * size
    end := start + size
    array := []int{}
    row := numStr[start:end]
    for _, v := range strings.Split(row, "") {
      value, _ := strconv.Atoi(v)
      array = append(array, value)
    }
    field = append(field, array)
  }

  return field
}

func printResult(r Result, size int, header bool) {
  if header {
    fmt.Println("")
    fmt.Println("n :", r.N)
    fmt.Println("(x, y) :", r.X+1, r.Y+1)
    fmt.Println("ok :", r.Ok)
    fmt.Println("value :", r.Value)
    fmt.Println("empty :", r.Empty)
    fmt.Println("candidate :", r.Candidate)
  }
  for i := 0; i < size; i++ {
    fmt.Println(r.Field[i])
  }
}

func counting(field [][]int, size int) int {
  n := 0
  for i := 0; i < size; i++ {
    for j := 0; j < size; j++ {
      if field[i][j] == 0 {
        n++
      }
    }
  }
  return n
}

func buildCandidate(size int) []int {
  candidate := []int{}
  for i := 0; i < size; i++ {
    candidate = append(candidate, i+1)
  }
  return candidate
}

func filter(field [][]int, x int, y int, size int, candidate []int) (int, bool, []int) {
  _candidate := make([]int, len(candidate))
  copy(_candidate, candidate)
  funcs := []func([][]int, int, int, int, []int) []int{filterVertical, filterHorizontal, filterBox}
  for _, cb := range funcs {
    _candidate = cb(field, x, y, size, _candidate)
    if len(_candidate) == 1 {
      return _candidate[0], true, _candidate
    }
  }

  return 0, false, _candidate
}

func filterVertical(field [][]int, x int, y int, size int, candidate []int) []int {
  _candidate := make([]int, len(candidate))
  copy(_candidate, candidate)
  for i := 0; i < size; i++ {
    value := field[i][x]
    if y != i && value != 0 {
      _candidate = remove(_candidate, value)
    }
  }
  return _candidate
}

func filterHorizontal(field [][]int, x int, y int, size int, candidate []int) []int {
  _candidate := make([]int, len(candidate))
  copy(_candidate, candidate)
  for i := 0; i < size; i++ {
    if x != i && field[y][i] != 0 {
      _candidate = remove(_candidate, field[y][i])
    }
  }
  return _candidate
}

func main() {
  const size = 9
  const maxTry = 1000
  flag.Parse()
  numStr := flag.Arg(0)
  // 1. コマンド引数から問題を読み込み
  field := load(numStr, size)

  // 2. 最初の状態を表示
  fmt.Println("")
  fmt.Println("[START]")
  empty := counting(field, size)
  result := Result{Field: field}
  printResult(result, size, false)
  n := 0
  // 8. 空の値がなくなるまでループ（無限ループ対策として、試行回数が1000回を超えたら失敗としてループを抜ける）
  for empty > 0 || n < maxTry {
    for i := 0; i < size; i++ {
      for j := 0; j < size; j++ {
        n++
        // 3. 左上のマスから順番に値を取得
        cursorValue := field[i][j]
        if cursorValue == 0 {
          candidate := buildCandidate(size)
          // 4. ルールを適用して値を取得
          value, ok, filteredCandidate := filter(field, j, i, size, candidate)
          // 5. 候補が絞れたらマスに結果を反映
          if ok {
            field[i][j] = value
            empty--
          }
          // 6. 処理結果を表示
          result = Result{N: n, X: j, Y: i, Ok: ok, Value: value, Candidate: filteredCandidate, Empty: empty, Field: field}
          printResult(result, size, true)
        }
      }
    }
  }

  // 8. 処理結果を表示
  if empty == 0 {
    fmt.Println("[END]")
  } else {
    fmt.Println("[FAILED]")
  }
  printResult(result, size, false)

}

func filter(field [][]int, x int, y int, size int, candidate []int) (int, bool, []int) {
  _candidate := make([]int, len(candidate))
  copy(_candidate, candidate)
  _candidate = filterVartical(field, x, y, size, _candidate)
  if len(_candidate) == 1 {
    return _candidate[0], true, _candidate
  }
  _candidate = filterHorizontal(field, x, y, size, _candidate)
  if len(_candidate) == 1 {
    return _candidate[0], true, _candidate
  }
  _candidate = filterBox(field, x, y, size, _candidate)
  if len(_candidate) == 1 {
    return _candidate[0], true, _candidate
  }

  return 0, false, _candidate
}