Update 743. 网络延迟时间.md

Author: CompetitiveLin

Shortest Path/743. 网络延迟时间.md

@@ -43,4 +43,45 @@
 *   `0 <= wi <= 100`
 *   所有 `(ui, vi)` 对都  **互不相同** （即，不含重复边）
 
----
+---
+
+Dijkstra算法 + 堆优化：模板题
+
+```java
+class Solution {
+    public int networkDelayTime(int[][] times, int n, int k) {
+        final int INF = Integer.MAX_VALUE / 2;
+        int[] dis = new int[n];
+        Arrays.fill(dis, INF);
+        int[][] g = new int[n][n];
+        for(int i = 0; i < n; i++){
+            Arrays.fill(g[i], INF);
+        }
+        for(int[] time: times){
+            g[time[0]- 1][time[1] - 1] = time[2];
+        }
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>((a,b) -> (a[0] - b[0]));	// [distance, node]
+        dis[k - 1] = 0;
+        minHeap.add(new int[] {0, k - 1});
+        while(!minHeap.isEmpty()){
+            int[] temp = minHeap.poll();
+            int temp_dis = temp[0], temp_node = temp[1];
+            if(temp_dis > dis[temp_node]) continue;
+            for(int i = 0; i < n; i++){
+                if(g[temp_node][i] != INF){
+                    if(temp_dis + g[temp_node][i] < dis[i]){
+                        minHeap.add(new int[] {temp_dis + g[temp_node][i], i});
+                        dis[i] = temp_dis + g[temp_node][i];
+                    }
+                }
+            }
+        }
+        int ans = 0;
+        for(int d: dis){
+            ans = Math.max(ans, d);
+        }
+        return ans == INF ? -1 : ans;
+    }
+}
+```
+