题目： 

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解析： 

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代码： 

private int ret;//返回周结果
    private int path;//枚举一个元素就异或进去
    public int subsetXORSum(int[] nums) {
        dfs(nums, 0);
        return ret;
    } 

    private void dfs(int[] nums, int pos){
        ret += path;
        for(int i = pos; i < nums.length; i++){
            path ^= nums[i];
            dfs(nums,i+1);
            //相同为0消除掉相同元素达到回复现场效果
            path ^= nums[i];
        }
    }