package correct import "github.com/01-edu/z01" const size = 8 // board is a chessboard composed of boolean squares, a true square means a queen is on it // a false square means it is a free square var board [size][size]bool // goodDirection check that there is no queen on the segment that starts at (x, y) // coordinates, points into the direction vector (vx, vy) and ends at the edge of the board func goodDirection(x, y, vx, vy int) bool { // x and y are still on board for 0 <= x && x < size && 0 <= y && y < size { if board[x][y] { // Not a good line : the square is already occupied return false } x += vx // Move x in the right direction y += vy // Move y in the right direction } // All clear return true } // goodSquare makes all the necessary line checks for the queens movements func goodSquare(x, y int) bool { return goodDirection(x, y, +0, -1) && goodDirection(x, y, +1, -1) && goodDirection(x, y, +1, +0) && goodDirection(x, y, +1, +1) && goodDirection(x, y, +0, +1) && goodDirection(x, y, -1, +1) && goodDirection(x, y, -1, +0) && goodDirection(x, y, -1, -1) } func printQueens() { x := 0 for x < size { y := 0 for y < size { if board[x][y] { // We have found a queen, let's print her y z01.PrintRune(rune(y) + '1') } y++ } x++ } z01.PrintRune('\n') } // tryX tries, for a given x (column) to find a y (row) so that the queen on (x, y) is a part // of the solution to the problem func tryX(x int) { y := 0 for y < size { if goodSquare(x, y) { // Since the square is good for the queen, let's put one on it: board[x][y] = true if x == size-1 { // x is the biggest possible x, it means that we just placed the last // queen on the board, so the solution is complete and we can print it printQueens() } else { // let's try to put another queen on the next empty x (column) tryX(x + 1) } // remove the queen of the board, to try other y values board[x][y] = false } y++ } } func EightQueens() { // try the first column tryX(0) }