LeetCode #40: Combination Sum II

Problem Statement

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

Each number in C may only be used once in the combination.

Note:

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

For example, given candidate set [10, 1, 2, 7, 6, 1, 5] and target 8,
A solution set is:

[  [1, 7],  [1, 2, 5],  [2, 6],  [1, 1, 6]]

Solution

class Solution(object):    def bt(self, candidates, target, res, ass, start_index):        if target == 0:            res.add(tuple(ass))        else:            for index in xrange(start_index, len(candidates)):                if candidates[index] > target:                    break                ass.append(candidates[index])                self.bt(candidates, target - candidates[index], res, ass, index + 1)                ass.pop()    def combinationSum2(self, candidates, target):        """        :type candidates: List[int]        :type target: int        :rtype: List[List[int]]        """        candidates.sort()        res = set()        self.bt(candidates, target, res, [], 0)        return [list(x) for x in res]