"""
Given a set of candidate numbers (C) (without duplicates) 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]
]
"""

class Solution(object):
    def combinationSum(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        #import copy
        def backtracking(start_index, candidates, remain, sub_solution, solution):
            if remain == 0:
                #solution.append(copy.deepcopy(sub_solution))
                solution.append(sub_solution)
                return
            for i in range(start_index, len(candidates)):
                if remain - candidates[i] >= 0:
                    backtracking(i, candidates, remain - candidates[i], sub_solution + [candidates[i]], solution)
        solution = []
        candidates = list(candidates)
        backtracking(0, candidates, target, [], solution)
        return solution

s = Solution()
print(s.combinationSum([2, 3, 6, 7], 7))

"""
Given a set of candidate numbers (C) (without duplicates) 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]
]
"""

class Solution(object):
    def combinationSum(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        #import copy
        def backtracking(start_index, candidates, remain, sub_solution, solution):
            if remain == 0:
                #solution.append(copy.deepcopy(sub_solution))
                solution.append(sub_solution)
                return
            for i in range(start_index, len(candidates)):
                if remain - candidates[i] >= 0:
                    backtracking(i, candidates, remain - candidates[i], sub_solution + [candidates[i]], solution)
        solution = []
        candidates = list(candidates)
        backtracking(0, candidates, target, [], solution)
        return solution

s = Solution()
print(s.combinationSum([2, 3, 6, 7], 7))

Given a set of candidate numbers (C) (without duplicates) 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] ] :type candidates: List[int]         :type target: int         :rtype: List[List[int]] #import copy #solution.append(copy.deepcopy(sub_solution))