Solution2.go

func combinationSum(candidates []int, target int) (ans [][]int) {
	sort.Ints(candidates)
	t := []int{}
	var dfs func(i, s int)
	dfs = func(i, s int) {
		if s == 0 {
			ans = append(ans, slices.Clone(t))
			return
		}
		if i >= len(candidates) || s < candidates[i] {
			return
		}
		dfs(i+1, s)
		t = append(t, candidates[i])
		dfs(i, s-candidates[i])
		t = t[:len(t)-1]
	}
	dfs(0, target)
	return
}