78 Subsets

https://leetcode.com/problems/subsets/#/description

Given a set ofdistinctintegers,nums, return all possible subsets.

Note:The solution set must not contain duplicate subsets.

For example,
Ifnums=[1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

分析及代码

每次不想做题又要凑数就用这种backtracking打发hahah

public List<List<Integer>> subsets(int[] nums) {
    List<List<Integer>> res = new ArrayList<>();
    for(int i = 0; i <= nums.length; i++) {
        generate(nums, i, res, new ArrayList<>(), 0);
    }
    return res;
}

private void generate(int[] nums, int n, List<List<Integer>> res, List<Integer> item, int index) {
    if(item.size() == n) {
        res.add(new ArrayList<>(item));
        return;
    }
    for(int i = index; i < nums.length; i++) {
        item.add(nums[i]);
        generate(nums, n, res, item, i + 1);
        item.remove(item.size() - 1);
    }
}