Solution.java

class Solution {
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        Arrays.sort(candidates);
        List<List<Integer>> result = new ArrayList<>();
        findTarget(target, candidates.length - 1, new ArrayList<>(), result, candidates);
        return result;
    }
    
    private void findTarget(int target, int lastElementIndex, List<Integer> current, List<List<Integer>> result, int[] candidates) {
        if (target == 0) {
            result.add(new ArrayList(current));
            return;
        }
        
        for (int i = lastElementIndex; i >= 0; i--) {
            int candidate = candidates[i];
            if (target < candidate) {
                continue;
            }
            
            current.add(candidates[i]);
            findTarget(target - candidate, i, current, result, candidates);
            current.remove(current.size() - 1);
        }
    }
}