From 3c9810e7de48bd6818bdbc3e357fc66d3a4edf83 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Fri, 24 Jan 2025 17:45:57 +0100
Subject: [PATCH] =?UTF-8?q?java:=20add=20=C2=AB802.=20Find=20Eventual=20Sa?=
=?UTF-8?q?fe=20States=C2=BB?=
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URL: https://leetcode.com/problems/find-eventual-safe-states/
Signed-off-by: Matej Focko <me@mfocko.xyz>
---
java/find-eventual-safe-states.java | 60 +++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)
create mode 100644 java/find-eventual-safe-states.java
diff --git a/java/find-eventual-safe-states.java b/java/find-eventual-safe-states.java
new file mode 100644
index 0000000..a611d62
--- /dev/null
+++ b/java/find-eventual-safe-states.java
@@ -0,0 +1,60 @@
+class Solution {
+ private static class DFS {
+ private int[][] graph;
+ private boolean[] visited;
+ private boolean[] open;
+
+ public DFS(int[][] graph) {
+ this.graph = graph;
+ visited = new boolean[graph.length];
+ open = new boolean[graph.length];
+ }
+
+ public boolean hasInCycle(int u) {
+ return open[u];
+ }
+
+ public boolean run(int u) {
+ if (open[u]) {
+ // found loop
+ return true;
+ }
+
+ if (visited[u]) {
+ // searched vertex
+ return false;
+ }
+
+ visited[u] = true;
+
+ open[u] = true;
+ for (var v : graph[u]) {
+ if (run(v)) {
+ // loops stay open
+ return true;
+ }
+ }
+ open[u] = false;
+
+ return false;
+ }
+ }
+
+ public List<Integer> eventualSafeNodes(int[][] graph) {
+ int n = graph.length;
+
+ var runner = new DFS(graph);
+ for (var i = 0; i < n; ++i) {
+ runner.run(i);
+ }
+
+ var safe = new ArrayList<Integer>();
+ for (var i = 0; i < n; ++i) {
+ if (!runner.hasInCycle(i)) {
+ safe.add(i);
+ }
+ }
+
+ return safe;
+ }
+}