[20251021] BOJ / P5 / 개코전쟁 / 이종환

Author: 0224LJH

0224LJH/202510/21 BOJ 개코전쟁.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.StringTokenizer;
+
+public class Main {
+	
+	static boolean[] visited;
+	static int nodeCnt,edgeCnt,ans;
+	static Node[] nodes;
+	static int[] cost;
+	
+	static class Node{
+		int num;
+		HashSet<Edge> edges = new HashSet<>();
+		ArrayList<Node> way = new ArrayList<>(); // 이 곳으로 오기위한 길 기록
+		
+		public Node(int num) {
+			this.num = num;
+		}
+	}
+	
+	static class Edge{
+		boolean isAlive = true;
+		Node from;
+		Node to;
+		int cost;
+		
+		public Edge(Node from, Node to, int cost) {
+			this.from = from;
+			this.to = to;
+			this.cost = cost;
+		}
+	}
+	
+    public static void main(String[] args) throws IOException {
+    	init();
+    	process();
+    	print();
+    }
+    
+    private static void init() throws IOException{
+    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    	StringTokenizer st = new StringTokenizer(br.readLine());
+    	nodeCnt = Integer.parseInt(st.nextToken());
+    	edgeCnt = Integer.parseInt(st.nextToken());
+    	ans = 0;
+    	
+    	visited = new boolean[nodeCnt+1];
+    	cost = new int[nodeCnt+1];
+    	nodes = new Node[nodeCnt+1];
+    	for (int i = 0; i <= nodeCnt; i++) {
+    		nodes[i] = new Node(i);
+    	}
+    	
+    	Arrays.fill(cost, Integer.MAX_VALUE);
+    	cost[1] = 0;
+    	
+    	
+    	
+    	for (int i = 0; i < edgeCnt; i++) {
+    		st = new StringTokenizer(br.readLine());
+    		Node n1 = nodes[Integer.parseInt(st.nextToken())];
+    		Node n2 = nodes[Integer.parseInt(st.nextToken())];
+    		int cost = Integer.parseInt(st.nextToken());
+    		
+    		n1.edges.add(new Edge(n1,n2,cost));
+    		n2.edges.add(new Edge(n2,n1,cost));
+    	}
+    }
+    
+    private static void process() {
+    	HashSet<Node> set =new HashSet<>();
+    	for (Node n: nodes) set.add(n);
+    	Node node = nodes[1];
+    	while (!set.isEmpty()) {
+    		set.remove(node);
+    		
+    		for (Edge e: node.edges) {
+    			Node to = e.to;
+    			if (cost[to.num] > cost[node.num] + e.cost) {
+    				cost[to.num] = cost[node.num] + e.cost;
+    				
+    				to.way = new ArrayList<>();
+    				to.way.addAll(node.way);
+    				to.way.add(node);
+    			}
+    		}
+    		
+    		int idx = -1;
+    		int min = Integer.MAX_VALUE;
+    		
+    		for (Node n: set) {
+//    			System.out.println(cost[n.num]);
+    			if (cost[n.num] < min) {
+    				min = cost[n.num];
+    				idx = n.num;
+    			}
+    		}
+    		if (idx == -1) break;
+    		node = nodes[idx];
+    		
+    		
+    	}
+    	
+    	
+    	ArrayList<Node> bestWay = nodes[nodeCnt].way;
+    	bestWay.add(nodes[nodeCnt]);
+    	int wayLen = bestWay.size();
+    	for (int i = 0; i < wayLen-1; i++) {
+    		Node cur = bestWay.get(i);
+    		Node next = bestWay.get(i+1);
+    		
+    		for (Edge e: cur.edges) {
+    			if (e.to.equals(next)) e.isAlive = false;
+    		}
+    		for (Edge e: next.edges) {
+    			if (e.to.equals(cur)) e.isAlive = false;
+    		}
+    		
+//    		System.out.println(cur.num + "->" + next.num);
+    		simulate();
+    		
+    		for (Edge e: cur.edges) {
+    			if (e.to.equals(next)) e.isAlive = true;
+    		}
+    		for (Edge e: next.edges) {
+    			if (e.to.equals(cur)) e.isAlive = true;
+    		}
+    	}
+    	
+    }
+    
+    private static void simulate() {
+    	HashSet<Node> set =new HashSet<>();
+    	for (Node n: nodes) set.add(n);
+    	
+    	Arrays.fill(cost, Integer.MAX_VALUE);
+    	cost[1] = 0;
+    	
+    	Node node = nodes[1];
+    	while (!set.isEmpty()) {
+    		set.remove(node);
+    		
+    		for (Edge e: node.edges) {
+    			if (!e.isAlive) continue;
+    			Node to = e.to;
+    			if (cost[to.num] > cost[node.num] + e.cost) {
+    				cost[to.num] = cost[node.num] + e.cost;
+    			}
+    		}
+    		
+    		int idx = -1;
+    		int min = Integer.MAX_VALUE;
+    		
+    		for (Node n: set) {
+//    			System.out.println(cost[n.num]);
+    			if (cost[n.num] < min) {
+    				min = cost[n.num];
+    				idx = n.num;
+    			}
+    		}
+    		if (idx == -1) break;
+    		node = nodes[idx];
+    		
+    		
+    	}
+//    	System.out.println(cost[nodeCnt]);
+    	ans = Math.max(ans, cost[nodeCnt]);
+    }
+    
+    private static void print() {
+    	System.out.println(ans);
+    }
+
+}
+```