Create 752-Open-the-lock.java

Author: SharmaTushar1

java/752-Open-the-lock.java

@@ -0,0 +1,48 @@
+//Simple BFS solution
+
+class Solution {
+    public int openLock(String[] deadends, String target) {
+        String start = "0000";
+        int ans = 0;
+        Queue<String> q = new LinkedList<>();
+        HashSet<String> visited = new HashSet<>();
+        //Add all the deadends in the visited set so we can ignore them and visited values altogether.
+        for (String s: deadends) 
+            visited.add(s);
+        q.offer(start);
+        while (!q.isEmpty()) {
+            int size =  q.size();
+            for (int j = 0; j<size; j++) {
+                String str = q.poll();
+                StringBuilder cur = new StringBuilder(str);
+                if (str.equals(target)) return ans;
+                if (!visited.contains(cur.toString())) {
+                    for (int i = 0; i<start.length(); i++) {
+                        //edge case for 0
+                        if (cur.charAt(i)=='0') {
+                            cur.setCharAt(i, '1');
+                            q.offer(cur.toString());
+                            cur.setCharAt(i, '9');
+                            q.offer(cur.toString());
+                        } else if (cur.charAt(i)=='9') { //edge case for 9
+                            cur.setCharAt(i, '0');
+                            q.offer(cur.toString());
+                            cur.setCharAt(i, '8');
+                            q.offer(cur.toString());
+                        } else {
+                            cur.setCharAt(i, ((char)(cur.charAt(i)+1)));
+                            q.offer(cur.toString());
+                            cur.setCharAt(i, ((char)(cur.charAt(i)-2)));
+                            q.offer(cur.toString());
+                        }
+                        visited.add(str);
+                        cur.setLength(0);
+                        cur.append(str);
+                    }
+                }
+            }
+            ans++;
+        }
+        return -1;
+    }
+}