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[Java] 1030. Travel Plan (30)-PAT甲级

1030. Travel Plan (30)

A traveler’s map gives the distances between cities along the highways, together with the cost of each highway. Now you are supposed to write a program to help a traveler to decide the shortest path between his/her starting city and the destination. If such a shortest path is not unique, you are supposed to output the one with the minimum cost, which is guaranteed to be unique.

Input Specification:

Each input file contains one test case. Each case starts with a line containing 4 positive integers N, M, S, and D, where N (<=500) is the number of cities (and hence the cities are numbered from 0 to N-1); M is the number of highways; S and D are the starting and the destination cities, respectively. Then M lines follow, each provides the information of a highway, in the format:

City1 City2 Distance Cost

where the numbers are all integers no more than 500, and are separated by a space.

Output Specification:

For each test case, print in one line the cities along the shortest path from the starting point to the destination, followed by the total distance and the total cost of the path. The numbers must be separated by a space and there must be no extra space at the end of output.

Sample Input

4 5 0 3

0 1 1 20

1 3 2 30

0 3 4 10

0 2 2 20

2 3 1 20

Sample Output

0 2 3 3 40

题目大意：求起点到终点的最短路径最短距离和花费，要求首先路径最短，其次花费最少，要输出完整路径

PS：感谢github用户 @fs19910227 提供的pull request～

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.PriorityQueue;
 
public class Main {
    static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
 
    static class Info {
        int distance, cost;
 
        Info(int distance, int cost) {
            this.distance = distance;
            this.cost = cost;
        }
    }
 
    static class Graph {
        private final int vertex, edges, end, start;
        private final Info[][] tables;
 
        Graph() throws IOException {
            String[] split = reader.readLine().split(" ");
            this.vertex = Integer.valueOf(split[0]);
            this.edges = Integer.valueOf(split[1]);
            this.start = Integer.valueOf(split[2]);
            this.end = Integer.valueOf(split[3]);
 
            tables = new Info[vertex][vertex];
            for (int i = 0; i < edges; i++) {
                String[] lineInfo = reader.readLine().split(" ");
                int s = Integer.valueOf(lineInfo[0]);
                int e = Integer.valueOf(lineInfo[1]);
                int distance = Integer.valueOf(lineInfo[2]);
                int cost = Integer.valueOf(lineInfo[3]);
                tables[s][e] = new Info(distance, cost);
                tables[e][s] = new Info(distance, cost);
            }
        }
 
        Node bfs() {
            Node node = new Node(start);
            boolean[] checkTable = new boolean[vertex];
            PriorityQueue<Node> queue = new PriorityQueue<>();
            queue.add(node);
            while (!queue.isEmpty()) {
                Node poll = queue.poll();
                if (poll.id == end) {
                    return poll;
                }
                checkTable[poll.id] = true;
                for (int i = 0; i < vertex; i++) {
                    Info info = tables[poll.id][i];
                    if (info != null && !checkTable[i]) {
                        Node newNode = new Node(i);
                        newNode.previous = poll;
                        newNode.distance = poll.distance + info.distance;
                        newNode.cost = poll.cost + info.cost;
                        queue.offer(newNode);
                    }
                }
            }
            return null;
        }
    }
 
    static class Node implements Comparable<Node> {
        int id, distance, cost;
        Node previous;
 
        Node(int id) {
            this.id = id;
        }
 
        @Override
        public int compareTo(Node o) {
            int compare = distance - o.distance;
            if (compare == 0) {
                compare = id - o.id;
            }
            return compare == 0 ? cost - o.cost : compare;
        }
    }
 
    public static void main(String[] args) throws IOException {
        Graph graph = new Graph();
        Node bfs = graph.bfs();
        LinkedList<String> list = new LinkedList<>();
        list.addFirst(String.valueOf(bfs.cost));
        list.addFirst(String.valueOf(bfs.distance));
        while (bfs != null) {
            list.addFirst(String.valueOf(bfs.id));
            bfs = bfs.previous;
        }
        int last = list.size() - 1;
        int start = 0;
        for (String o : list) {
            System.out.printf("%s%s", o, start == last ? "/n" : " ");
            start++;
        }
    }
}

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原文 https://www.liuchuo.net/archives/5000

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