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LeetCode

Backtracking

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class Solution {
    private void util(int[] arr, int target, List<List<Integer>> res, List<Integer> ls, int start) {
        if (target < 0) {
            return;
        } else if (target == 0) {
            res.add(new ArrayList(ls));
            return;
        } else {
            for (int i = start; i < arr.length; i++) {
                if (i > start && arr[i] == arr[i - 1]){
                    continue;
                }    
                ls.add(arr[i]);
                util(arr, target - arr[i], res, ls, i + 1);
                ls.remove(ls.size() - 1);
            }
        }
    }

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

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