YAPC::EU 2018 Glasgow Update!

Task/Solve-a-Hidato-puzzle/Go/solve-a-hidato-puzzle.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+    "fmt"
+    "sort"
+    "strconv"
+    "strings"
+)
+
+var board [][]int
+var start, given []int
+
+func setup(input []string) {
+    /* This task is not about input validation, so
+       we're going to trust the input to be valid */
+    puzzle := make([][]string, len(input))
+    for i := 0; i < len(input); i++ {
+        puzzle[i] = strings.Fields(input[i])
+    }
+    nCols := len(puzzle[0])
+    nRows := len(puzzle)
+    list := make([]int, nRows*nCols)
+    board = make([][]int, nRows+2)
+    for i := 0; i < nRows+2; i++ {
+        board[i] = make([]int, nCols+2)
+        for j := 0; j < nCols+2; j++ {
+            board[i][j] = -1
+        }
+    }
+    for r := 0; r < nRows; r++ {
+        row := puzzle[r]
+        for c := 0; c < nCols; c++ {
+            switch cell := row[c]; cell {
+            case "_":
+                board[r+1][c+1] = 0
+            case ".":
+                break
+            default:
+                val, _ := strconv.Atoi(cell)
+                board[r+1][c+1] = val
+                list = append(list, val)
+                if val == 1 {
+                    start = append(start, r+1, c+1)
+                }
+            }
+        }
+    }
+    sort.Ints(list)
+    given = make([]int, len(list))
+    for i := 0; i < len(given); i++ {
+        given[i] = list[i]
+    }
+}
+
+func solve(r, c, n, next int) bool {
+    if n > given[len(given)-1] {
+        return true
+    }
+
+    back := board[r][c]
+    if back != 0 && back != n {
+        return false
+    }
+
+    if back == 0 && given[next] == n {
+        return false
+    }
+
+    if back == n {
+        next++
+    }
+
+    board[r][c] = n
+    for i := -1; i < 2; i++ {
+        for j := -1; j < 2; j++ {
+            if solve(r+i, c+j, n+1, next) {
+                return true
+            }
+        }
+    }
+
+    board[r][c] = back
+    return false
+}
+
+func printBoard() {
+    for _, row := range board {
+        for _, c := range row {
+            switch {
+            case c == -1:
+                fmt.Print(" . ")
+            case c > 0:
+                fmt.Printf("%2d ", c)
+            default:
+                fmt.Print("__ ")
+            }
+        }
+        fmt.Println()
+    }
+}
+
+func main() {
+    input := []string{
+        "_ 33 35 _ _ . . .",
+        "_ _ 24 22 _ . . .",
+        "_ _ _ 21 _ _ . .",
+        "_ 26 _ 13 40 11 . .",
+        "27 _ _ _ 9 _ 1 .",
+        ". . _ _ 18 _ _ .",
+        ". . . . _ 7 _ _",
+        ". . . . . . 5 _",
+    }
+    setup(input)
+    printBoard()
+    fmt.Println("\nFound:")
+    solve(start[0], start[1], 1, 0)
+    printBoard()
+}