Problem
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:
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:
Input: candidates = [2,5,2,1,2], target = 5,
A solution set is:
[
[1,2,2],
[5]
]
Solution
Backtracking problem.
Use DFS.
- make a choice
- call dfs recursive for all rest choices
- revert the choice
Notes:
- sort the candidates and avoid the duplicates
- return early when the target is smaller than 0
class Solution:
def combinationSum(self, candidates, target):
self.ans = []
candidates.sort()
self.dfs(candidates, 0, [], target)
return self.ans
def dfs(self, candidates, index, path, target):
if target < 0:
return
if target == 0:
self.ans.append(list(path))
for i in range(index, len(candidates)):
if i > index and candidates[i] == candidates[i-1]:
continue
path.append(candidates[i])
self.dfs(i+1, candidates, path, target-candidates[i])
path.pop()