[20250407] BOJ / P4 / 산책 (large) / 권혁준

Author: oncsr

khj20006/202504/07 BOJ P4 산책 (large).md

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+```java
+
+import java.util.*;
+import java.io.*;
+
+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 = new StringTokenizer("");
+
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static String nextToken() throws Exception {
+		while(!st.hasMoreTokens()) nextLine();
+		return st.nextToken();
+	}
+	static int nextInt() throws Exception { return Integer.parseInt(nextToken()); }
+	static long nextLong() throws Exception { return Long.parseLong(nextToken()); }
+	static double nextDouble() throws Exception { return Double.parseDouble(nextToken()); }
+	static void bwEnd() throws Exception {bw.flush();bw.close();}
+	
+	// Additional field
+	
+	static int N, M, S, E;
+	static List<int[]>[] V;
+	static boolean[] vis; 
+	
+	static final int INF = (int)1e9 + 5;
+	
+	public static void main(String[] args) throws Exception {
+			
+		ready();
+		solve();
+	
+		bwEnd();
+		
+	}
+	
+	static void ready() throws Exception{
+		
+		N = nextInt();
+		M = nextInt();
+		V = new List[N+1];
+		for(int i=1;i<=N;i++) V[i] = new ArrayList<>();
+		for(int i=0;i<M;i++) {
+			int a = nextInt(), b = nextInt(), c = nextInt();
+			V[a].add(new int[] {b,c});
+			V[b].add(new int[] {a,c});
+		}
+		for(int i=1;i<=N;i++) Collections.sort(V[i], (a,b) -> a[0]-b[0]);
+		S = nextInt();
+		E = nextInt();
+		vis = new boolean[N+1];
+		
+	}
+	
+	static void solve() throws Exception{
+		
+		int ans = 0;
+		{
+			PriorityQueue<int[]> Q = new PriorityQueue<>((a,b) -> {
+				if(a[0] == b[0]) return a[1]-b[1];
+				return a[0]-b[0];
+			});
+			int[] D = new int[N+1];
+			Arrays.fill(D, INF);
+			Q.offer(new int[] {0,E});
+			D[E] = 0;
+			while(!Q.isEmpty()) {
+				int[] now = Q.poll();
+				int d = now[0], n = now[1];
+				if(d > D[n]) continue;
+				for(int[] next:V[n]) {
+					int i = next[0], c = next[1];
+					if(D[i] > d+c) {
+						D[i] = d+c;
+						Q.offer(new int[] {D[i],i});
+					}
+				}
+			}
+			ans += D[S];
+			int g = S;
+			while(g != E) {
+				for(int[] i:V[g]) if(D[g] == i[1] + D[i[0]]) {
+					g = i[0];
+					break;
+				}
+				if(g != E) vis[g] = true;
+			}
+			
+		}
+		
+		
+		PriorityQueue<int[]> Q = new PriorityQueue<>((a,b) -> {
+			if(a[0] == b[0]) return a[1]-b[1];
+			return a[0]-b[0];
+		});
+		int[] D = new int[N+1];
+		Arrays.fill(D, INF);
+		Q.offer(new int[] {0,E});
+		D[E] = 0;
+		while(!Q.isEmpty()) {
+			int[] now = Q.poll();
+			int d = now[0], n = now[1];
+			if(d > D[n]) continue;
+			for(int[] next:V[n]) if(!vis[next[0]]) {
+				int i = next[0], c = next[1];
+				if(D[i] > d+c) {
+					D[i] = d+c;
+					Q.offer(new int[] {D[i],i});
+				}
+			}
+		}
+		bw.write((ans + D[S]) + "\n");
+		
+	}
+	
+}
+
+```