design phone directory

fishercoder1534 · fishercoder1534 · commit c782f61d8118 · 2016-11-23T11:56:46.000-08:00
diff --git a/MEDIUM/src/medium/DesignPhoneDirectory.java b/MEDIUM/src/medium/DesignPhoneDirectory.java
@@ -0,0 +1,53 @@
+package medium;
+
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Set;
+
+public class DesignPhoneDirectory {
+
+    private class PhoneDirectory {
+        private Queue<Integer> phoneDir;
+        private Set<Integer> used;
+        /**
+         * Initialize your data structure here
+         * 
+         * @param maxNumbers
+         *            - The maximum numbers that can be stored in the phone directory.
+         */
+        public PhoneDirectory(int maxNumbers) {
+            phoneDir = new LinkedList();
+            int number = 0;
+            while (maxNumbers-- > 0){
+                phoneDir.add(number++);
+            }
+            used = new HashSet();
+        }
+
+        /**
+         * Provide a number which is not assigned to anyone.
+         * 
+         * @return - Return an available number. Return -1 if none is available.
+         */
+        public int get() {
+            if (phoneDir.peek() == null) return -1;
+            int newNumber = phoneDir.poll();
+            used.add(newNumber);
+            return newNumber;
+        }
+
+        /** Check if a number is available or not. */
+        public boolean check(int number) {
+            return !used.contains(number);
+        }
+
+        /** Recycle or release a number. */
+        public void release(int number) {
+            if (used.remove(number)) {
+                phoneDir.add(number);
+            }
+        }
+    }
+
+}
diff --git a/README.md b/README.md
@@ -29,6 +29,7 @@
 |388|[Longest Absolute File Path](https://leetcode.com/problems/longest-absolute-file-path/)|[Solution](../../blob/master/MEDIUM/src/medium/LongestAbsoluteFilePath.java)| O(n)|O(d) | Medium| Stack
 |387|[First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/)|[Solution](../../blob/master/EASY/src/easy/FirstUniqueCharacterinaString.java)| O(n)|O(n) | Easy| HashMap
 |386|[Lexicographical Numbers](https://leetcode.com/problems/lexicographical-numbers/)|[Solution](../../blob/master/MEDIUM/src/medium/LexicographicalNumbers.java)| O(n)|O(1) | Medium| 
+|379|[Design Phone Directory](https://leetcode.com/problems/design-phone-directory/)|[Solution](../../blob/master/MEDIUM/src/medium/DesignPhoneDirectory.java)| O(1)|O(n) | Medium| 
 |374|[Guess Number Higher or Lower](https://leetcode.com/problems/guess-number-higher-or-lower/)|[Solution](../../blob/master/EASY/src/easy/GuessNumberHigherorLower.java)| O(logn)|O(1) | Easy| Binary Search
 |350|[Intersection of Two Arrays II](https://leetcode.com/problems/intersection-of-two-arrays-ii/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArraysII.java)| O(m+n)|O((m+n)) could be optimized | Easy| HashMap, Binary Search
 |349|[Intersection of Two Arrays](https://leetcode.com/problems/intersection-of-two-arrays/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArrays.java)| O(m+n)|O(min(m,n)) | Easy| Two Pointers, Binary Search
