Create Dijkstra.java

Author: versatile0010

4주차/힌트/Dijkstra.java

@@ -0,0 +1,81 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static ArrayList<Node>[] graph;
+    static int v;
+    static int e;
+    static int s;
+    static int [] dist;
+
+    public static void main(String[] args) throws IOException {
+        System.setIn(new FileInputStream("src/input.txt"));
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        StringTokenizer stk;
+
+        // graph init
+        stk = new StringTokenizer(br.readLine());
+        v = Integer.parseInt(stk.nextToken());
+        e = Integer.parseInt(stk.nextToken());
+
+        s = Integer.parseInt(br.readLine());
+
+        graph = new ArrayList[v + 1];
+        for (int i = 0; i <= v; i++)
+            graph[i] = new ArrayList<>();
+
+        for (int i = 0; i < e; i++) {
+            stk = new StringTokenizer(br.readLine());
+            int a = Integer.parseInt(stk.nextToken());
+            int b = Integer.parseInt(stk.nextToken());
+            int w = Integer.parseInt(stk.nextToken());
+
+            graph[a].add(new Node(b, w));
+        }
+        dijkstra(s);
+
+        for(int i = 1; i <=v; i++){
+            if(dist[i] != Integer.MAX_VALUE){
+                bw.write(dist[i]+"\n");
+            } else bw.write("INF\n");
+        }
+
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    static class Node implements Comparable<Node> {
+        int to;
+        int w;
+
+        public Node(int to, int w) {
+            this.to = to;
+            this.w = w;
+        }
+
+        @Override
+        public int compareTo(Node o) {
+            return this.w - o.w;
+        }
+    }
+
+    static void dijkstra(int start){
+        PriorityQueue<Node> pq = new PriorityQueue<>();
+        dist = new int [v+1];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[start] = 0;
+
+        pq.add(new Node(start, 0));
+        while(!pq.isEmpty()){
+            Node now = pq.poll();
+            for(Node iter : graph[now.to]){
+                if(dist[iter.to] > dist[now.to] + iter.w){
+                    dist[iter.to] = dist[now.to] + iter.w; // update
+                    pq.add(new Node(iter.to, dist[iter.to]));
+                }
+            }
+        }
+    }
+}