[Java] 백준 - 1916번: 최소비용 구하기

9월 8일(금) - 그래프와 순회 (1916번)

1916번: 최소비용 구하기

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문제점

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.StringTokenizer;

public class Main {

    private static final int INF = Integer.MAX_VALUE / 16;
    static int[][] map;
    static int[] distance, visited;
    public static void main(String[] args) throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;

        int N = Integer.parseInt(br.readLine());
        int M = Integer.parseInt(br.readLine());

        map = new int[N+1][N+1];
        distance = new int[N+1];
        visited = new int[N+1];
        for(int i=0; i<N; i++)
        {
            for(int j=0; j<N; j++)
            {
                map[i][j] = INF;
            }
        }

        for(int i=0; i<M; i++)
        {
            st = new StringTokenizer(br.readLine());
            int start = Integer.parseInt(st.nextToken());
            int end = Integer.parseInt(st.nextToken());
            int weight = Integer.parseInt(st.nextToken());

            if(map[start][end] > weight)
            {
                map[start][end] = weight;
            }
        }

        st = new StringTokenizer(br.readLine());
        int target_start = Integer.parseInt(st.nextToken());
        int target_end = Integer.parseInt(st.nextToken());

        dijkstra(N, target_start, target_end);

    }

    static void dijkstra(int N, int start, int end){
        for(int i=1; i<=N; i++)
        {
            distance[i] = INF;
        }

        distance[start] = 0;
        for(int i=1; i<=N; i++)
        {
            int min = INF;

            for(int j=1; j<=N; j++)
            {
                if(visited[j] == 0 && min > distance[j])
                {
                    min = distance[j];
                    start = j;
                }
            }

            visited[start] = 1;
            for(int next = 1; next<=N; next++)
            {
                if(map[start][next] != INF && distance[next] > distance[start] + map[start][next])
                {
                    distance[next] = distance[start] + map[start][next];
                }
            }
        }

        System.out.println(distance[end]);
    }
}

1. C언어 풀이 활용하여 작성

-> 예제1을 입력하는 경우, 0이 출력됨

-> 추후 다시 풀어봐야함

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풀이

(풀이출처 -> https://velog.io/@lifeisbeautiful/Java-백준-1916번-최소비용-구하기-with-자바)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.*;

public class Main {

    private static final int INF = Integer.MAX_VALUE / 16;
    static List<ArrayList<Node>> list;
    static int distance[];
    static int N;

    static class Node implements Comparable<Node>{
        int nodeNum;
        int weight;

        public Node(int nodeNum, int weight){
            this.nodeNum = nodeNum;
            this.weight = weight;
        }

        @Override
        public int compareTo(Node o)
        {
            return weight - o.weight;
        }
    }

    public static void main(String[] args) throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;

        N = Integer.parseInt(br.readLine());
        int M = Integer.parseInt(br.readLine());

        list = new ArrayList<>();
        distance = new int[N+1];
        Arrays.fill(distance, INF);

        for(int i=0; i<=N; i++)
        {
            list.add(new ArrayList<>());
        }

        for(int i=0; i<M; i++)
        {
            st = new StringTokenizer(br.readLine());

            int start = Integer.parseInt(st.nextToken());
            int end = Integer.parseInt(st.nextToken());
            int weight = Integer.parseInt(st.nextToken());

            list.get(start).add(new Node(end, weight));
        }

        st = new StringTokenizer(br.readLine());

        int target_start = Integer.parseInt(st.nextToken());
        int target_end = Integer.parseInt(st.nextToken());

        System.out.println(dijkstra(target_start, target_end));
    }

    static int dijkstra(int start, int end){
        PriorityQueue<Node> pq = new PriorityQueue<Node>();
        boolean visited[] = new boolean[N+1];

        distance[start] = 0;
        pq.offer(new Node(start, 0));

        while (!pq.isEmpty())
        {
            Node queNode = pq.poll();
            int start_nodeNum = queNode.nodeNum;

            if(!visited[start_nodeNum])
            {
                visited[start_nodeNum] = true;

                for(Node node : list.get(start_nodeNum))
                {
                    if(!visited[node.nodeNum] && distance[node.nodeNum] > (distance[start_nodeNum] + node.weight))
                    {
                        distance[node.nodeNum] = distance[start_nodeNum] + node.weight;
                        pq.offer(new Node(node.nodeNum, distance[node.nodeNum]));
                    }
                }
            }
        }

        return distance[end];
    }
}

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