From 0df65e062882245b95f957514f2d17c51e2c9566 Mon Sep 17 00:00:00 2001
From: anjali9811 <72162196+anjali9811@users.noreply.github.com>
Date: Thu, 1 Oct 2020 01:10:53 +0530
Subject: [PATCH] Add files via upload

---
 keys and rooms.cpp | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 keys and rooms.cpp

diff --git a/keys and rooms.cpp b/keys and rooms.cpp
new file mode 100644
index 0000000..85419e3
--- /dev/null
+++ b/keys and rooms.cpp	
@@ -0,0 +1,23 @@
+class Solution {
+    public boolean canVisitAllRooms(List<List<Integer>> rooms) {
+        boolean[] seen = new boolean[rooms.size()];
+        seen[0] = true;
+        Stack<Integer> stack = new Stack();
+        stack.push(0);
+
+        //At the beginning, we have a todo list "stack" of keys to use.
+        //'seen' represents at some point we have entered this room.
+        while (!stack.isEmpty()) { // While we have keys...
+            int node = stack.pop(); // Get the next key 'node'
+            for (int nei: rooms.get(node)) // For every key in room # 'node'...
+                if (!seen[nei]) { // ...that hasn't been used yet
+                    seen[nei] = true; // mark that we've entered the room
+                    stack.push(nei); // add the key to the todo list
+                }
+        }
+
+        for (boolean v: seen)  // if any room hasn't been visited, return false
+            if (!v) return false;
+        return true;
+    }
+}