DAY19：leetcode #39 Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

• All numbers (including target) will be positive integers.
• The solution set must not contain duplicate combinations.

For example, given candidate set [2, 3, 6, 7] and target 7, 
A solution set is: 

[  [7],  [2, 2, 3]]

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import copyclass Solution(object):    def combinationSum(self, candidates, target):        """        :type candidates: List[int]        :type target: int        :rtype: List[List[int]]        """        tree = []        result = set()        candidates_len = len(candidates)        candidates.sort()        while(sum(tree) < target):            tree.append(candidates[0])        while(True):            if sum(tree) == target:                #print tree                result.add(tuple(sorted(copy.deepcopy(tree))))                #print result                pos = candidates_len                flag = True                while pos == candidates_len:                    del tree[-1]                    if len(tree) == 0:                        flag = False                        break                    pos = candidates.index(tree[-1]) + 1                if not flag:                    break                tree[-1] = candidates[candidates.index(tree[-1])+1]            elif sum(tree) > target:                pos = candidates_len                flag = True                while pos == candidates_len:                    del tree[-1]                    if len(tree) == 0:                        flag = False                        break                    pos = candidates.index(tree[-1]) + 1                if not flag:                    break                tree[-1] = candidates[candidates.index(tree[-1])+1]            else:                while(sum(tree) < target):                    tree.append(candidates[0])                pos = candidates.index(tree[-1]) + 1                flag = True                while pos == candidates_len:                    del tree[-1]                    if len(tree) == 0:                        flag = False                        break                    pos = candidates.index(tree[-1]) + 1                if not flag:                    break                tree[-1] = candidates[candidates.index(tree[-1])+1]        result = list(result)        for i in range(len(result)):            result[i] = list(result[i])        return result