## [LeetCode] 39. Combination Sum_Medium tag: backtracking

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:

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

Example 2:

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

Code

```class Solution:
def combinationSum(self, nums, target):
ans = []
nums.sort()
self.search(nums, ans, [], 0, target)
return ans

def search(self, nums, ans, temp, pos, target):
if target == 0:
ans.append(temp)
for i in range(pos, len(nums)):
if nums[i] > target:  # because we sorted the nums
break
self.search(nums, ans, temp + [nums[i]], i , target - nums[i]) # keep i instead of i + 1, because we can use one number unlimited times```