40. Combination Sum II leetcode Python 2016 new season

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.
• Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
• 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] 

class Solution(object):
    def bfs(self, candidates, target, result, valuelist, start):
        if target == 0 and valuelist not in result:
            return result.append(valuelist)
        for index in range(start, len(candidates)):
            if target < candidates[index]:
                return
            self.bfs(candidates, target - candidates[index], result, valuelist + [candidates[index]], index + 1)
    def combinationSum2(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        candidates.sort()
        result = []
        self.bfs(candidates, target, result, [], 0)
        return result