/**
 * Beispiel aus
 *
 * - Algorithmen und Datenstrukturen für Dummies
 *   - von Andreas Gogol-Döring und Thomas Letschert
 *   - Verlag Wiley-VCH; Oktober 2019
 *  - Kapitel 11, Probleme totschlagen
 *
 * @author A. Gogol-Döring, Th. Letschert
 */

import Foundation

struct AuD_11_03_EightQueensExhaustiveSearch {

    static func Ok(_ board: [Int]) -> Bool {
        for i in 0 ..< board.count {
            for j in i + 1 ..< board.count {
                let x = board[i]
                let y = board[j]
                let d = j - i
                if (x == y || y == x - d || y == x + d) {
                    return false
                }
            }
        }
        return true
    }

    /*
     * Es lebe die Kraft der geschachtelten Schleifen.
     */

    static func EightQueens() -> [Int] {
        for p0 in 0 ..< 8 {
            for p1 in 0 ..< 8 {
                for p2 in 0 ..< 8 {
                    for p3 in 0 ..< 8 {
                        for p4 in 0 ..< 8 {
                            for p5 in 0 ..< 8 {
                                for p6 in 0 ..< 8 {
                                    for p7 in 0 ..< 8 {
                                        if Ok([p0, p1, p2, p3, p4, p5, p6, p7]) {
                                            return [p0, p1, p2, p3, p4, p5, p6, p7]
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
        return [] // keine Loesung
    }

    static func run() {
        print(EightQueens())
    }

}