ccf历年第四题java解答之-201403-4-最优配餐

使用bfs求解（运行超时，80分）

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import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

class Node{
    public int x;
    public int y;
    public int step;

    public Node(int x, int y, int step) {
        this.x = x;
        this.y = y;
        this.step = step;
    }
}

public class Main{
    private static int n;
    private static int totalCount;
    private static Queue<Node> queue = new LinkedList<>();
    private static int[][] counts;
    private static boolean[][] visited;

    public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);

        String[] firstLine = scanner.nextLine().split(" ");
        n  = Integer.parseInt(firstLine[0]);
        int m = Integer.parseInt(firstLine[1]);
        int k = Integer.parseInt(firstLine[2]);
        int d = Integer.parseInt(firstLine[3]);

        visited = new boolean[n + 1][n + 1];
        counts = new int[n + 1][n + 1];

        for(int i = 0; i < m; i++){
            String[] line = scanner.nextLine().split(" ");
            int x = Integer.parseInt(line[0]);
            int y = Integer.parseInt(line[1]);
            visited[x][y] = true;
            queue.add(new Node(x, y, 0));
        }

        for(int i = 0; i < k; i++){
            String[] line = scanner.nextLine().split(" ");
            int x = Integer.parseInt(line[0]);
            int y = Integer.parseInt(line[1]);
            int c = Integer.parseInt(line[2]);

            if(counts[x][y] == 0)
                totalCount++;
            counts[x][y] += c;

        }

        for(int i = 0; i < d; i++){
            String[] line = scanner.nextLine().split(" ");
            int x = Integer.parseInt(line[0]);
            int y = Integer.parseInt(line[1]);
            visited[x][y] = true;
        }
        scanner.close();

        System.out.println(bfs());
    }

    private static long bfs(){
        long step = 0;
        int[][] dirs = {{-1, 0}, {1, 0}, {0, 1}, {0, -1}};

        while (!queue.isEmpty()){
            if(totalCount == 0)
                return step;

            Node front = queue.poll();

            for(int i = 0; i < dirs.length; i++){
                int x = front.x + dirs[i][0];
                int y = front.y + dirs[i][1];

                if(x < 1 || x > n || y < 1 || y > n)
                    continue;

                if(visited[x][y])
                    continue;

                visited[x][y] = true;
                Node node = new Node(x, y, front.step + 1);
                queue.add(node);

                if(counts[x][y] > 0){
                    totalCount--;
                    step += counts[x][y] * node.step;

                    if(totalCount == 0)
                        return step;
                }
            }

        }

        return step;
    }

}