Merge pull request qiyuangong#2 from WGierke/patch-1

Solve 216: Combination Sum III, contributed by @WGierke.

Author: qiyuangong

README.md

@@ -77,6 +77,7 @@ Remember solutions are only solutions to given problems. If you want full study
 | 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/200_Number_of_Islands.py) | 1. Quick union find, O(nlogn) and O(n^2)<br>2. BFS with marks, O(n^2) and O(1) |
 | 206 | [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/206_Reverse_Linked_List.py) | 1. Stack, O(n) and O(n)<br>2. Traverse on prev and curr, then curr.next = prev, O(n) and O(1)<br>3. Recursion, O(n) and O(1) | 
 | 213 | [House Robber II](https://leetcode.com/problems/house-robber-ii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/213_House_Robber_II.py) | f(k) = max(f(k – 2) + num[k], max(dp[0~ls-2],dp[1~ls-1], O(n) and O(1)|
+| 216 | [Combination Sum III](https://leetcode.com/problems/combination-sum-iii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/216_Combination_Sum_III.py) | Generate all combinations of length k and keep those that sum to n|
 | 217 | [Contains Duplicate](https://leetcode.com/problems/contains-duplicate/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/217_Contains_Duplicate.py) | 1. Set and compare length<br>2. Sort and check i,i +1|
 | 219 | [Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/219_Contains_Duplicate_II.py) | 1. Brute force<br> 2. Maintenance a set that contains previous k numbers, and check if curr in set |
 | 220 | [Contains Duplicate III](https://leetcode.com/problems/contains-duplicate-iii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/220_Contains_Duplicate_III.py) | 1. Sort and binary Search <br>2. Bucket sort |

python/216_Combination_Sum_III.py

@@ -0,0 +1,9 @@
+import itertools as it
+ class Solution(object):
+    def combinationSum3(self, k, n):
+        """
+        :type k: int
+        :type n: int
+        :rtype: List[List[int]]
+        """
+        return list(it.ifilter(lambda x: sum(x) == n, list(it.combinations(range(1, 10), k))))