packagemedium;

importjava.util.ArrayList;

importjava.util.List;

importutils.CommonUtils;

publicclassGenerateParentheses {

publicList<String>generateParenthesis(intn) {

List<String>result =newArrayList();

backtrack(result,"",0,0,n);

returnresult;

}

voidbacktrack(List<String>result,Stringstr,intleft,intright,intmax){

if(str.length() ==max*2){

result.add(str);

return;

}

if(left <max){

backtrack(result,str+"(",left+1,right,max);

}

if(right <left){

backtrack(result,str+")",left,right+1,max);

}

}

publicstaticvoidmain(String...args){

GenerateParenthesestest =newGenerateParentheses();

intn =3;

List<String>result =test.generateParenthesis(n);

CommonUtils.print(result);

}

}

|43|[Multiply Strings](https://leetcode.com/problems/multiply-strings/)|[Solution]|||Medium

|24|[Swap Nodes in Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/)|[Solution](../../blob/master/EASY/src/easy/SwapNodesinPairs.java)|O(n)|O(1)|Easy| Recursion, LinkedList

|23|[Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)|[Solution](../../blob/master/HARD/src/hard/MergeKSortedList.java)|O(n*logk)|O(logk)|Hard|Heap

|22|[Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)|[Solution](../../blob/master/MEDIUM/src/medium/GenerateParentheses.java)|TBD|O(n)|Medium|Backtracking

|21|[Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)|[Solution](../../blob/master/EASY/src/easy/MergeTwoSortedLists.java)|O(n)|O(1)|Easy|

|20|[Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)|[Solution](../../blob/master/EASY/src/easy/ValidParentheses.java)|O(n)|O(n)|Easy|Stack

|17|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/)|[Solution](../../blob/master/MEDIUM/src/medium/LetterCombinationsofaPhoneNumber.java)|O(n*4^n)|O(n)|Medium|Backtracking