java: add «1514. Path with Maximum Probability»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/path-with-maximum-probability.java

@@ -0,0 +1,57 @@
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.PriorityQueue;
+
+class Solution {
+  private record Edge(int v, double p) {}
+
+  private static Map<Integer, List<Edge>> makeGraph(int[][] edges, double[] p) {
+    Map<Integer, List<Edge>> graph = new HashMap<>();
+
+    for (int i = 0; i < edges.length; ++i) {
+      var u = edges[i][0];
+      var v = edges[i][1];
+      var prob = p[i];
+
+      graph.computeIfAbsent(u, k -> new ArrayList<>()).add(new Edge(v, prob));
+      graph.computeIfAbsent(v, k -> new ArrayList<>()).add(new Edge(u, prob));
+    }
+
+    return graph;
+  }
+
+  private record Entry(double probability, int u) {}
+
+  public double maxProbability(
+      int n, int[][] edges, double[] succProb, int startNode, int endNode) {
+    var graph = makeGraph(edges, succProb);
+    var maxProb = new double[n];
+
+    PriorityQueue<Entry> q =
+        new PriorityQueue<>(Comparator.comparingDouble(Entry::probability).reversed());
+
+    maxProb[startNode] = 1;
+    q.add(new Entry(maxProb[startNode], startNode));
+
+    while (!q.isEmpty()) {
+      var candidate = q.poll();
+      if (candidate.u() == endNode) {
+        return candidate.probability();
+      }
+
+      for (var edge : graph.getOrDefault(candidate.u(), new ArrayList<>())) {
+        var possibleProbability = candidate.probability() * edge.p();
+
+        if (possibleProbability > maxProb[edge.v()]) {
+          maxProb[edge.v()] = possibleProbability;
+          q.add(new Entry(maxProb[edge.v()], edge.v()));
+        }
+      }
+    }
+
+    return 0;
+  }
+}