Combination Sum II

## Description

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

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

return doCombinationSum(candidates, target)
}

func doCombinationSum(candidates []int, target int) [][]int {
res := [][]int{}

if len(candidates) == 0 {
return res
}

t := target - candidates[0]

if t == 0 {
res = append(res, []int{candidates[0]})
} else if t > 0 {
res = doCombinationSum(candidates[1:], t)
for i, v := range res {
res[i] = append([]int{candidates[0]}, v...)
}
}

// 为了去重
for len(candidates) > 1 && candidates[0] == candidates[1] {
candidates = candidates[1:]
}

res = append(res, doCombinationSum(candidates[1:], target)...)

return res
}``````