[Graph] baekjoon-1753

Author: Seogeurim

README.md

@@ -163,6 +163,7 @@
 | :-: | :-: | :---------------------------------------------------- | :--- |
 | 01  |     | [Baekjoon-11724 연결 요소의 개수](./src/Graph/P11724) |      |
 | 02  |     | [Baekjoon-1707 이분 그래프](./src/Graph/P1707)        |      |
+| 03  |     | [Baekjoon-1753 최단경로](./src/Graph/P1753)        |   Dijkstra   |
 
 ### Union-Find
 

src/Graph/P1753/Main.java

@@ -0,0 +1,65 @@
+package Graph.P1753;
+
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    final static int INF = Integer.MAX_VALUE;
+    static int V, E, K;
+    static ArrayList<Node>[] graph;
+    static int[] D;
+
+    public static void main(String[] args) throws Exception {
+        System.setIn(new FileInputStream("src/Graph/P1753/input.txt"));
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        V = stoi(st.nextToken());
+        E = stoi(st.nextToken());
+        K = stoi(br.readLine());
+
+        graph = new ArrayList[V+1];
+        for (int i = 1; i <= V; i++) graph[i] = new ArrayList<>();
+        while (E-- > 0) {
+            st = new StringTokenizer(br.readLine());
+            int u = stoi(st.nextToken()), v = stoi(st.nextToken()), w = stoi(st.nextToken());
+            graph[u].add(new Node(v, w));
+        }
+
+        D = new int[V+1];
+        Arrays.fill(D, INF);
+        PriorityQueue<Node> pq = new PriorityQueue<>(((o1, o2) -> o1.dist - o2.dist));
+
+        pq.offer(new Node(K, 0));
+        D[K] = 0;
+        while (!pq.isEmpty()) {
+            Node current = pq.poll();
+            if (D[current.idx] < current.dist) continue;
+            for (int i = 0; i < graph[current.idx].size(); i++) {
+                Node next = graph[current.idx].get(i);
+                if (D[next.idx] > D[current.idx] + next.dist) {
+                    D[next.idx] = D[current.idx] + next.dist;
+                    pq.offer(new Node(next.idx, D[next.idx]));
+                }
+            }
+        }
+
+        for (int i = 1; i <= V; i++) {
+            if (D[i] == INF) System.out.println("INF");
+            else System.out.println(D[i]);
+        }
+    }
+
+    private static int stoi(String s) { return Integer.parseInt(s); }
+
+    static class Node {
+        int idx;
+        int dist;
+
+        public Node(int idx, int dist) {
+            this.idx = idx;
+            this.dist = dist;
+        }
+    }
+}

src/Graph/P1753/README.md

@@ -0,0 +1,8 @@
+## [baekjoon-1753] 최단경로
+
+![image](https://user-images.githubusercontent.com/22045163/106621109-93515900-65b5-11eb-8fcf-ded496c53a11.png)
+
+### 다익스트라 알고리즘 - Priority Queue를 이용한 개선 알고리즘
+
+- 그래프 정보를 이차원 배열에 저장하면 **메모리 초과**
+- 단순 배열로 다음 방문 정점을 고르면 **시간 초과**

src/Graph/P1753/input.txt

@@ -0,0 +1,8 @@
+5 6
+1
+5 1 1
+1 2 2
+1 3 3
+2 3 4
+2 4 5
+3 4 6