Commit 0719b16

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solves combinations

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`@@ -70,6 +70,7 @@`
`70`	`70`	`\| 73 \| [Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes) \| [![Java](assets/java.png)](src/SetMatrixZeroes.java) \| \|`
`71`	`71`	`\| 74 \| [Search a 2D Matrix](https://leetcode.com/problems/search-a-2d-matrix) \| [![Java](assets/java.png)](src/SearchA2DMatrix.java) \| \|`
`72`	`72`	`\| 75 \| [Sort Colors](https://leetcode.com/problems/sort-colors) \| [![Java](assets/java.png)](src/SortColors.java) \| \|`
	`73`	`+\| 77 \| [Combinations](https://leetcode.com/problems/combinations) \| [![Java](assets/java.png)](src/Combinations.java) \| \|`
`73`	`74`	`\| 83 \| [Remove Duplicates from Sorted List](https://leetcode.com/problems/remove-duplicates-from-sorted-list) \| [![Java](assets/java.png)](src/RemoveDuplicatesFromSortedList.java) [![Python](assets/python.png)](python/remove_duplicates_from_linked_list.py) \| \|`
`74`	`75`	`\| 88 \| [Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array) \| [![Java](assets/java.png)](src/MergeSortedArray.java) [![Python](assets/python.png)](python/merge_sorted_array.py) \| \|`
`75`	`76`	`\| 94 \| [Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/) \| [![Java](assets/java.png)](src/BinaryTreeInorderTraversal.java) [![Python](assets/python.png)](python/binary_tree_inorder_traversal.py) \| \|`

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`@@ -0,0 +1,31 @@`
	`1`	`+// https://leetcode.com/problems/combinations`
	`2`	`+// T: O(k * 2^n)`
	`3`	`+// S: O(k)`
	`4`	`+`
	`5`	`+import java.util.ArrayList;`
	`6`	`+import java.util.LinkedList;`
	`7`	`+import java.util.List;`
	`8`	`+`
	`9`	`+public class Combinations {`
	`10`	`+ public List<List<Integer>> combine(int n, int k) {`
	`11`	`+ final List<List<Integer>> result = new ArrayList<>();`
	`12`	`+ createCombinations(n, k, result);`
	`13`	`+ return result;`
	`14`	`+ }`
	`15`	`+`
	`16`	`+ private void createCombinations(int n, int k, List<List<Integer>> result) {`
	`17`	`+ addCombinations(n, 1, k, result, new LinkedList<>());`
	`18`	`+ }`
	`19`	`+`
	`20`	`+ private void addCombinations(int n, int current, int length, List<List<Integer>> result, LinkedList<Integer> combination) {`
	`21`	`+ if (combination.size() == length) {`
	`22`	`+ result.add(new ArrayList<>(combination));`
	`23`	`+ return;`
	`24`	`+ }`
	`25`	`+ if (current > n) return;`
	`26`	`+ combination.add(current);`
	`27`	`+ addCombinations(n, current + 1, length, result, combination);`
	`28`	`+ combination.removeLast();`
	`29`	`+ addCombinations(n, current + 1, length, result, combination);`
	`30`	`+ }`
	`31`	`+}`

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