39. Combination Sum[M]

https://leetcode.com/problems/combination-sum/

Description

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]
]

Constraints:

  • 1 <= candidates.length <= 30
  • 1 <= candidates[i] <= 200
  • Each element of candidate is unique.
  • 1 <= target <= 500

Solution

1

40. Combination Sum II[M]

https://leetcode.com/problems/combination-sum-ii/

Description

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

Each number in candidates 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.

Example 1:

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Input: candidates = [10,1,2,7,6,1,5], target = 8,
A solution set is:
[
  [1, 7],
  [1, 2, 5],
  [2, 6],
  [1, 1, 6]
]

Example 2:

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Input: candidates = [2,5,2,1,2], target = 5,
A solution set is:
[
  [1,2,2],
  [5]
]

Solution

1

216. Combination Sum III[M]

https://leetcode.com/problems/combination-sum-iii/

Description

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.

Note:

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

Example 1:

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Input: k = 3, n = 7
Output: [[1,2,4]]

Example 2:

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Input: k = 3, n = 9
Output: [[1,2,6], [1,3,5], [2,3,4]]

Solution

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import itertools as it
class Solution:
    def combinationSum3(self, k: int, n: int) -> List[List[int]]:
        return list(filter(lambda x: sum(x) == n, list(it.combinations(range(1, 10), k))))