[20260324] BOJ / G3 / 역사 / 이인희

Author: LiiNi-coder

LiiNi-coder/202603/24 BOJ 역사.md

@@ -0,0 +1,74 @@
+```java
+import java.util.*;
+import java.io.*;
+public class Main{
+	/*
+	* 순서 그래프 생성
+	* 간선 최적화 안하고 그냥 바로 최단거리 알고리즘 돌림
+	*
+	* */
+	private static List<List<Integer>> Graph;
+	private static int N, M;
+	private static int MAX = Integer.MAX_VALUE / 2;
+	public static void main(String[] args) throws IOException{
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		N = Integer.parseInt(st.nextToken());
+		M = Integer.parseInt(st.nextToken());
+		Graph = new ArrayList<>();
+		for(int i = 0; i < N; i++) Graph.add(new ArrayList<>());
+		for(int i = 0; i < M; i++){
+			st = new StringTokenizer(br.readLine());
+			int s = Integer.parseInt(st.nextToken()) - 1;
+			int e = Integer.parseInt(st.nextToken()) - 1;
+
+			Graph.get(s).add(e);
+		}
+
+		//인접리스트 -> 인접행렬
+		int[][] dists = new int[N][N];
+		for(int r = 0; r < N; r++)
+			for(int c = 0; c < N; c++)
+				dists[r][c] = MAX;
+		for(int s = 0; s < N; s++){
+			for(int e : Graph.get(s)){
+				dists[s][e] = 1;
+			}
+		}
+		for(int i = 0; i < N; i++)
+			dists[i][i] = 0;
+
+		//플로이드워셜
+		for(int k = 0; k < N; k++)
+			for(int s = 0; s < N; s++)
+				for(int e = 0; e < N; e++){
+					int nw = dists[s][k] + dists[k][e];
+					if(nw < dists[s][e])
+						dists[s][e] = nw;
+				}
+
+		// for(int[] row : dists)
+		// 	System.out.println(Arrays.toString(row));
+		int query = Integer.parseInt(br.readLine());
+		for(int i = 0; i < query; i++){
+			st = new StringTokenizer(br.readLine());
+			int l = Integer.parseInt(st.nextToken()) - 1;
+			int r = Integer.parseInt(st.nextToken()) -1;
+
+			boolean lr = (dists[l][r] > 0 && dists[l][r] < MAX);
+			boolean rl = (dists[r][l] > 0 && dists[r][l] < MAX );
+			// System.out.println(lr + ", " + rl);
+			String answer;
+			if(lr)
+				answer = "-1";
+			else if(rl)
+				answer = "1";
+			else
+				answer = "0";
+			System.out.println(answer);
+		}
+
+		br.close();
+	}
+}
+```