BOJ_11657 : 타임머신 (벨만 포드)

Author: spring0913

Diff for: week7/BOJ_11657(타임머신).java

@@ -0,0 +1,55 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    public static int city;
+    public static List<List<int[]>> graph;
+    public static long[] dist;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        city = Integer.parseInt(st.nextToken());
+        int bus = Integer.parseInt(st.nextToken());
+        graph = new ArrayList<>();
+        dist = new long[city+1];
+        for(int i=0; i<=city; i++) {
+            graph.add(new ArrayList<>());
+            dist[i] = Long.MAX_VALUE;
+        }
+        for(int i=0; i<bus; i++) {
+            st = new StringTokenizer(br.readLine());
+            int v1 = Integer.parseInt(st.nextToken());
+            int v2 = Integer.parseInt(st.nextToken());
+            int cost = Integer.parseInt(st.nextToken());
+            graph.get(v1).add(new int[]{v2, cost});
+        }
+        bellmanFord(1);
+    }
+
+    public static void bellmanFord(int start) {
+        dist[start] = 0;
+        for(int i=1; i<=city; i++) {
+            for(int j=1; j<=city; j++) {
+                List<int[]> list = graph.get(j);
+                for(int k=0; k<list.size(); k++) {
+                    int nextV = list.get(k)[0];
+                    int nextCost = list.get(k)[1];
+                    if(dist[j] != Long.MAX_VALUE && dist[nextV] > dist[j] + nextCost) {
+                        dist[nextV] = dist[j] + nextCost;
+
+                        // city(정점 개수)번째 반복에 갱신되는 값이 있으면 음수 사이클 존재
+                        if(i == city) {
+                            System.out.println("-1");
+                            return;
+                        }
+                    }
+                }
+            }
+        }
+        for(int i=2; i<=city; i++) {
+            System.out.println((dist[i] == Long.MAX_VALUE) ? "-1" : dist[i]);
+        }
+    }
+}