题目链接：LeetCode40

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class Solution {
    List<List<Integer>> rs = new ArrayList<>();
    LinkedList<Integer> path = new LinkedList<>();
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        Arrays.sort(candidates);
        backTracking(candidates, target, 0, 0);
        return rs;
    }

    void backTracking(int[] candidates, int target, int sum, int startIdx) {
        if (sum > target) {
            return;
        }
        if (sum == target) {
            rs.add(new ArrayList<Integer>(path));
            return;
        }

        for (int i = startIdx; i < candidates.length; i++) {
            if (i > startIdx && candidates[i] == candidates[i - 1]) {
                continue;
            }
            sum += candidates[i];
            path.add(candidates[i]);
            backTracking(candidates, target, sum, i + 1);
            path.removeLast();
            sum -= candidates[i];
        }
    }
}