Solution.java

class Solution {
    private List<List<Integer>> ans;
    private int[] candidates;
    private int target;

    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        ans = new ArrayList<>();
        Arrays.sort(candidates);
        this.target = target;
        this.candidates = candidates;
        dfs(0, 0, new ArrayList<>());
        return ans;
    }

    private void dfs(int u, int s, List<Integer> t) {
        if (s > target) {
            return;
        }
        if (s == target) {
            ans.add(new ArrayList<>(t));
            return;
        }
        for (int i = u; i < candidates.length; ++i) {
            if (i > u && candidates[i] == candidates[i - 1]) {
                continue;
            }
            t.add(candidates[i]);
            dfs(i + 1, s + candidates[i], t);
            t.remove(t.size() - 1);
        }
    }
}