leetcode

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problem 39

39. Combination Sum

Medium

Given a set of candidate numbers (candidates) (without duplicates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target.

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

Note:

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

Example 1:

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Input: candidates = [2,3,6,7], target = 7,
A solution set is:
[
  [7],
  [2,2,3]
]

Example 2:

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Input: candidates = [2,3,5], target = 8,
A solution set is:
[
  [2,2,2,2],
  [2,3,3],
  [3,5]
]

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class Solution:
    def combinationSum(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        
        rests = [[] for _ in range(target)]
        
        for num in candidates:
            if num > target:
                continue
            else:
                rests[target - num].append([num])
            for cur_rest in range(target - 1, num - 1, -1):
                for result in rests[cur_rest]:
                    rests[cur_rest - num].append(result + [num])
        
        return rests[0]