First commit

.gitignore

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+.idea

LICENSE

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+MIT License
+
+Copyright (c) 2022 Adrien
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# sudoku-solver
+This tool tries to find a solution for a given sudoku grid.

go.mod

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+module gitea.illuad.fr/adrien/sudoku-solver
+
+go 1.17

main.go

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+package main
+
+import "fmt"
+
+var field = [9][9]int{
+	{5, 3, 0, 0, 7, 0, 0, 0, 0},
+	{6, 0, 0, 1, 9, 5, 0, 0, 0},
+	{0, 9, 8, 0, 0, 0, 0, 6, 0},
+	{8, 0, 0, 0, 6, 0, 0, 0, 3},
+	{4, 0, 0, 8, 0, 3, 0, 0, 1},
+	{7, 0, 0, 0, 2, 0, 0, 0, 6},
+	{0, 6, 0, 0, 0, 0, 2, 8, 0},
+	{0, 0, 0, 4, 1, 9, 0, 0, 5},
+	{0, 0, 0, 0, 8, 0, 0, 7, 9},
+}
+
+func draw() {
+	for _, row := range field {
+		fmt.Println(row)
+	}
+	fmt.Println()
+}
+
+func canPut(x int, y int, value int) bool {
+	return !alreadyInVertical(x, y, value) &&
+		!alreadyInHorizontal(x, y, value) &&
+		!alreadyInSquare(x, y, value)
+}
+
+func alreadyInVertical(x int, y int, value int) bool {
+	for i := range [9]int{} {
+		if field[i][x] == value {
+			return true
+		}
+	}
+	return false
+}
+
+func alreadyInHorizontal(x int, y int, value int) bool {
+	for i := range [9]int{} {
+		if field[y][i] == value {
+			return true
+		}
+	}
+	return false
+}
+
+func alreadyInSquare(x int, y int, value int) bool {
+	sx, sy := int(x/3)*3, int(y/3)*3
+	for dy := range [3]int{} {
+		for dx := range [3]int{} {
+			if field[sy+dy][sx+dx] == value {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func next(x int, y int) (int, int) {
+	nextX, nextY := (x+1)%9, y
+	if nextX == 0 {
+		nextY = y + 1
+	}
+	return nextX, nextY
+}
+
+func solve(x int, y int) bool {
+	if y == 9 {
+		return true
+	}
+	if field[y][x] != 0 {
+		return solve(next(x, y))
+	} else {
+		for i := range [9]int{} {
+			var v = i + 1
+			if canPut(x, y, v) {
+				field[y][x] = v
+				if solve(next(x, y)) {
+					return true
+				}
+				field[y][x] = 0
+			}
+		}
+		return false
+	}
+}
+
+func main() {
+	fmt.Println("Grid to be completed:")
+	draw()
+	if solve(0, 0) {
+		fmt.Println("I found a solution, see below")
+		draw()
+	} else {
+		fmt.Println("I did not find a solution")
+	}
+}