[20250206] BOJ / 골드2 / The Other Way / 권혁준

khj20006/202502/06 BOJ G2 The Other Way.md

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+```java
+
+import java.util.*;
+import java.io.*;
+
+class Edge{
+	int x;
+	long c;
+	Edge(int x, long c){
+		this.x = x;
+		this.c = c;
+	}
+}
+
+class Element {
+	long dist, cnt;
+	int node;
+	Element(long dist, long cnt, int node){
+		this.dist = dist;
+		this.cnt = cnt;
+		this.node = node;
+	}
+}
+
+class Main {
+
+	// IO field
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	static StringTokenizer st;
+
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static int nextInt() {return Integer.parseInt(st.nextToken());}
+	static long nextLong() {return Long.parseLong(st.nextToken());}
+	static void bwEnd() throws Exception {bw.flush();bw.close();}
+
+	// Additional field
+	static List<Edge>[] V;
+	static long[] D;
+	static long[] C;
+	static int N, M, S, E;
+	static long mod = (long)1e9 + 9, INF = 1234567890123456789L;
+
+	public static void main(String[] args) throws Exception {
+
+		ready();
+		solve();
+
+		bwEnd();
+	}
+
+	static void ready() throws Exception{
+
+		nextLine();
+		N = nextInt();
+		M = nextInt();
+		S = nextInt();
+		E = nextInt();
+		V = new ArrayList[N+1];
+		D = new long[N+1];
+
+		Arrays.fill(D, INF);
+		C = new long[N+1];
+		for(int i=1;i<=N;i++) V[i] = new ArrayList<>();
+
+		for(int i=0;i<M;i++) {
+			nextLine();
+			int a = nextInt(), b = nextInt();
+			long c = nextLong();
+			V[a].add(new Edge(b,c));
+			V[b].add(new Edge(a,c));
+		}
+
+	}
+
+	static void solve() throws Exception{
+
+		dijkstra(S);
+		bw.write(C[E]%mod + "\n");
+
+	}
+
+	static void dijkstra(int start) {
+
+		D[start] = 0;
+		C[start] = 1;
+		PriorityQueue<Element> PQ = new PriorityQueue<>((a,b) -> {
+			if(a.dist == b.dist) return 0;
+			if(a.dist < b.dist) return -1;
+			return 1;
+		});
+		PQ.offer(new Element(0,1,start));
+		while(!PQ.isEmpty()) {
+			Element now = PQ.poll();
+			if(now.dist > D[now.node]) continue;
+			for(Edge e : V[now.node]) {
+				if(D[e.x] > now.dist + e.c) {
+					D[e.x] = now.dist + e.c;
+					C[e.x] = C[now.node]; 
+					PQ.offer(new Element(D[e.x], C[e.x], e.x));
+				}
+				else if(D[e.x] == now.dist + e.c) {
+					C[e.x] = (C[e.x] + C[now.node]) % mod; 
+				}
+			}
+		}
+
+	}
+
+}
+
+```