[20250908] BOJ / G5 / 최소 비용 구하기 / 이종환

0224LJH/202509/08 BOJ 최소비용 구하기.md

@@ -0,0 +1,95 @@
+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+
+public class Main {
+	static int cityCnt, busCnt,start,goal;
+	static int[] distance;
+	static boolean[] visited;
+	static Node[] nodes;
+	static PriorityQueue<Node> pq = new PriorityQueue<>();
+
+	static class Node implements Comparable<Node>{
+		int num;
+		Map<Integer, Integer> costs = new HashMap<>();
+
+		public Node(int num) {
+			this.num = num;
+		}
+
+		@Override
+		public int compareTo(Node o) {
+			return Integer.compare(distance[this.num], distance[o.num]);
+		}
+	}
+
+
+    public static void main(String[] args) throws NumberFormatException, IOException {
+		init();
+		process();
+		print();
+    }
+
+    public static void init() throws NumberFormatException, IOException {
+    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    	cityCnt = Integer.parseInt(br.readLine());
+    	busCnt = Integer.parseInt(br.readLine());
+    	nodes = new Node[cityCnt+1];
+    	distance = new int[cityCnt+1];
+    	visited = new boolean[cityCnt+1];
+    	for (int i = 0; i <= cityCnt; i++) {
+    		nodes[i] = new Node(i);
+    	}
+
+    	for (int i = 0; i < busCnt; i++) {
+    		StringTokenizer st = new StringTokenizer (br.readLine());
+    		int from = Integer.parseInt(st.nextToken());
+    		int to = Integer.parseInt(st.nextToken());
+    		int cost = Integer.parseInt(st.nextToken());
+
+    		if (nodes[from].costs.containsKey(to)) {
+    			int smaller = Math.min(cost, nodes[from].costs.get(to));
+    			nodes[from].costs.replace(to, smaller);
+    		} else {
+    			nodes[from].costs.put(to, cost);
+    		}
+
+    	}
+
+    	StringTokenizer st = new StringTokenizer(br.readLine());
+    	start = Integer.parseInt(st.nextToken());
+    	goal = Integer.parseInt(st.nextToken());
+
+    	Arrays.fill(distance, Integer.MAX_VALUE/2);
+    	distance[start] = 0;
+    }
+
+    public static void process() {
+    	pq.add(nodes[start]);
+
+    	while(!pq.isEmpty()) {
+    		Node n = pq.poll();
+    		if (visited[n.num]) continue;
+    		visited[n.num] = true;
+
+    		for (int to: n.costs.keySet()) {
+    			if(visited[to]) continue;
+    			int cost = n.costs.get(to);
+    			int nDistance = distance[n.num] + cost;
+    			if (distance[to] > nDistance) {
+    				distance[to] = nDistance;
+    				pq.add(nodes[to]);
+    			}
+    		}
+
+    	}
+
+    }
+
+    public static void print() {
+    	System.out.println(distance[goal]);
+    }
+}
+```