Matematické Fórum

import java.lang.Math;
import java.util.Random;


public class SZ8D {
    static int broadSize = 40;
    static int tries = 100;

    static Random rand = new Random();

    static int cost(int[] solution) {
        int cost = 0;
        for (int i = 0; i < broadSize; i++) {
            for (int j = (i+1); j < broadSize; j++) {
                if (solution[i] == solution[j]) cost++;
                if (solution[i] == solution[j] + (j-i)) cost++;
                if (solution[i] == solution[j] - (j-i)) cost++;
            }
        }
        return cost;        
    }
    
    static int[] neighbor(int[] solution) {
        int column = rand.nextInt(broadSize);
        int row = rand.nextInt(broadSize);
        int[] returnSolution = solution.clone();
        returnSolution[column] = row;
        return returnSolution;    
    }
    
    static Boolean accept(int[] actual, int[] neighbor, double temp) {
        int diff = cost(neighbor) - cost(actual);
        if (diff < 0) {return true;}
        return rand.nextDouble() < Math.pow(Math.E,-diff/temp);
        
    }
    
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] current = new int[broadSize];
        for (int i = 0; i < broadSize; i++) {
            current[i] = rand.nextInt(broadSize);
        }
        long startAt = System.currentTimeMillis();
        for (int j = 0; j < tries; j++) {
            for (int i = 0; i < 10000; i++) {
                double temperature = 100.0 / (i + 100);
                int[] neighbor = neighbor(current);
                if (accept(current,neighbor,temperature)) {
                    current = neighbor;
                }
                if (cost(current) == 0) {
                    System.out.print("Try #" + Integer.toString(j) + "\n");
                    String Solution = "Solution ";
                    for (int k = 0; k < broadSize;k++) {
                        Solution = Solution + Integer.toString(current[k]) + " ";
                    }
                    Solution = Solution + " found in " + Integer.toString(i) + " iterations and " + Long.toString(System.currentTimeMillis() - startAt) + " ms. \n";
                    System.out.print(Solution);
                    return;
                }
                
            }
        }

    }

}