The following question is taken from Leetcode entitled ‘Combination Sum’
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.
- All numbers (including target) will be positive integers.
- The solution set must not contain duplicate combinations.
Input: candidates = [2,3,6,7], target = 7, A solution set is: [ , [2,2,3] ]
Input: candidates = [2,3,5], target = 8, A solution set is: [ [2,2,2,2], [2,3,3], [3,5] ]
To solve this problem, I applied dynamic programming, particularly bottom up 2D tabulation approach. The method is quite similar to 0/1 knapsack problem, that is, whether we want to use an element in candidates or not.
The following is my code:
class Solution: def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]: if not len(candidates): return 0 dp = [  + *target for _ in range(len(candidates) + 1)] for row in range(1, len(candidates) + 1): for col in range(1, target+1): dp[row][col] += dp[row - 1][col] if col - candidates[row-1] >= 0: dp[row][col] += dp[row][col - candidates[row-1]] print(dp[-1][-1])
However, my codes above do not give solution set. Instead, it gives the number of elements in solution set.
I attempted to generate solution set from my codes above but to no avail. Can anyone help me?