packagemedium;

importjava.util.HashSet;

importjava.util.LinkedList;

importjava.util.Queue;

importjava.util.Set;

publicclassDesignPhoneDirectory {

privateclassPhoneDirectory {

privateQueue<Integer>phoneDir;

privateSet<Integer>used;

publicPhoneDirectory(intmaxNumbers) {

phoneDir =newLinkedList();

intnumber =0;

while (maxNumbers-- >0){

phoneDir.add(number++);

}

used =newHashSet();

}

publicintget() {

if (phoneDir.peek() ==null)return -1;

intnewNumber =phoneDir.poll();

used.add(newNumber);

returnnewNumber;

}

publicbooleancheck(intnumber) {

return !used.contains(number);

}

publicvoidrelease(intnumber) {

if (used.remove(number)) {

phoneDir.add(number);

}

}

}

}

|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