Leetcode78——Subsets

文章作者:Tyan
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1. 问题描述

Given a set of distinct integers, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

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

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

2. 求解

递归法

这道题类似于数组的组合问题,可以用递归法求解。N个数中每个数都分为要与不要两种情况,求解的过程如下图。递归的边界条件为N个数都遍历完了。

递归过程

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public class Solution {
public static List<List<Integer>> result = new ArrayList<List<Integer>>();
public List<List<Integer>> subsets(int[] nums) {
result.clear();
result.add(new ArrayList<Integer>());
combination(nums, 0, new ArrayList<Integer>());
return result;
}
public void combination(int[] nums, int index, List<Integer> list) {
if(index == nums.length) {
return;
}
combination(nums, index + 1, new ArrayList<Integer>(list));
list.add(nums[index]);
result.add(list);
combination(nums, index + 1, new ArrayList<Integer>(list));
}
}
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