更新0094.城市间货物运输I-SPFA Java版本解法

Author: learnerInTheFirstStage

problems/kamacoder/0094.城市间货物运输I-SPFA.md

@@ -352,6 +352,77 @@ SPFA（队列优化版Bellman_ford） 在理论上 时间复杂度更胜一筹
 ## 其他语言版本
 
 ### Java 
+```Java
+import java.util.*;
+
+public class Main {
+
+    // Define an inner class Edge
+    static class Edge {
+        int from;
+        int to;
+        int val;
+        public Edge(int from, int to, int val) {
+            this.from = from;
+            this.to = to;
+            this.val = val;
+        }
+    }
+
+    public static void main(String[] args) {
+        // Input processing
+        Scanner sc = new Scanner(System.in);
+        int n = sc.nextInt();
+        int m = sc.nextInt();
+        List<List<Edge>> graph = new ArrayList<>();
+
+        for (int i = 0; i <= n; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        for (int i = 0; i < m; i++) {
+            int from = sc.nextInt();
+            int to = sc.nextInt();
+            int val = sc.nextInt();
+            graph.get(from).add(new Edge(from, to, val));
+        }
+
+        // Declare the minDist array to record the minimum distance form current node to the original node
+        int[] minDist = new int[n + 1];
+        Arrays.fill(minDist, Integer.MAX_VALUE);
+        minDist[1] = 0;
+
+        // Declare a queue to store the updated nodes instead of traversing all nodes each loop for more efficiency
+        Queue<Integer> queue = new LinkedList<>();
+        queue.offer(1);
+
+        // Declare a boolean array to record if the current node is in the queue to optimise the processing
+        boolean[] isInQueue = new boolean[n + 1];
+
+        while (!queue.isEmpty()) {
+            int curNode = queue.poll();
+            isInQueue[curNode] = false; // Represents the current node is not in the queue after being polled
+            for (Edge edge : graph.get(curNode)) {
+                if (minDist[edge.to] > minDist[edge.from] + edge.val) { // Start relaxing the edge
+                    minDist[edge.to] = minDist[edge.from] + edge.val;
+                    if (!isInQueue[edge.to]) { // Don't add the node if it's already in the queue
+                        queue.offer(edge.to);
+                        isInQueue[edge.to] = true;
+                    }
+                }
+            }
+        }
+        
+        // Outcome printing
+        if (minDist[n] == Integer.MAX_VALUE) {
+            System.out.println("unconnected");
+        } else {
+            System.out.println(minDist[n]);
+        }
+    }
+}
+
+```
 
 ### Python