 # Backtracking - 39. Combination Sum

39. 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.

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:
[
,
[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]
]
``````

``````func combinationSum(candidates []int, target int) [][]int {

var res [][]int

if candidates == nil || len(candidates) == 0 {
return res
}
dfs(&res, []int{}, candidates, target, 0)
return res
}

func dfs(res *[][]int, temp []int, nums []int, target int, start int) {
if target < 0 {
return
}
if target == 0 {
*res = append(*res, append([]int{}, temp...))
}

for i := start; i < len(nums); i++ {
temp = append(temp, nums[i]);
dfs(res, temp, nums, target - nums[i], i)
temp = temp[:len(temp)-1]
}
}
``````

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