taixingbi

Combination.py

https://leetcode.com/problemset/all/?search=Combination%20Sum
candidates without duplicates: 39 / 
                                      78 sub sets / 254. Factor Combinations
                                                  
candidates with duplicates: 40 / 267. Palindrome Permutation II
combinations of k numbers: 216
output number of possible combinations:  377 
others： 10. Regular Expression Matching / 294. Flip Game II / 291. Word Pattern II / 51. N-Queens /52. N-Queens II / 351. Android Unlock Patterns