# Backtracking - 40. Combination Sum II

40. Combination Sum II

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]
]
``````

``````func combinationSum2(candidates []int, target int) [][]int {

var res [][]int
if candidates == nil || len(candidates) == 0 {
return res
}
sort.Ints(candidates)
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++ {
if i != start && nums[i] == nums[i-1] {
continue
}
temp = append(temp, nums[i]);
dfs(res, temp, nums, target - nums[i], i+1)
temp = temp[:len(temp)-1]
}
}
``````

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