给定一个无重复元素的数组 candidates 和一个目标数 target ，找出 candidates 中所有可以使数字和为 target 的组合。
candidates 中的数字可以无限制重复被选取。
说明：
所有数字（包括 target）都是正整数。
解集不能包含重复的组合。
示例 1:
输入: candidates = [2,3,6,7], target = 7,
所求解集为:
[
[7],
[2,2,3]
]
示例 2:
输入: candidates = [2,3,5], target = 8,
所求解集为:
[
[2,2,2,2],
[2,3,3],
[3,5]
]
func combinationSum(candidates []int, target int) [][]int {
sort.Ints(candidates)
res := [][]int{}
solution := []int{}
var helper func([]int, int)
helper = func( solution []int, target int) {
if target == 0 {
tmp := make([]int, len(solution))
copy(tmp, solution)
res = append(res, tmp)
}
for i := 0;i < len(candidates);i++{
if candidates[i] <= target{
solution = append(solution,candidates[i])
helper(solution,target-candidates[i])
solution = solution[:len(solution)-1]
}
}
}
helper(solution, target)
return res
}
