# 2022-06-05

## [78. Subsets](https://leetcode.com/problems/subsets/)

### Description

Given an integer array `nums` of **unique** elements, return *all possible subsets (the power set)*.

The solution set **must not** contain duplicate subsets. Return the solution in **any order**.

**Example 1:**

```
Input: nums = [1,2,3]
Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]
```

**Example 2:**

```
Input: nums = [0]
Output: [[],[0]]
```

**Constraints:**

* `1 <= nums.length <= 10`
* `-10 <= nums[i] <= 10`
* All the numbers of `nums` are **unique**.

### Solution

#### Approach #0

```go
func subsets(nums []int) (ans [][]int) {
    n := len(nums)
    for p := 0; p < 1<<n; p++ {
        var a []int
        for i, num := range nums {
            if p>>i&1 > 0 {
                a = append(a, num)
            }
        }
        ans = append(ans, a)
    }
    return
}
```

#### Approach #1

```go
func subsets(nums []int) (ans [][]int) {
    n := len(nums)
    var tmp []int
    var dfs func(int)
    dfs = func(cur int) {
        if cur == n {
            ans = append(ans, append([]int(nil), tmp...))
            return
        }
        tmp = append(tmp, nums[cur])
        dfs(cur + 1)
        tmp = tmp[:len(tmp)-1]
        dfs(cur + 1)
    }
    dfs(0)
    return
}
```

## [90. Subsets II](https://leetcode.com/problems/subsets-ii/)

### Description

Given an integer array `nums` that may contain duplicates, return *all possible subsets (the power set)*.

The solution set **must not** contain duplicate subsets. Return the solution in **any order**.

**Example 1:**

```
Input: nums = [1,2,2]
Output: [[],[1],[1,2],[1,2,2],[2],[2,2]]
```

**Example 2:**

```
Input: nums = [0]
Output: [[],[0]]
```

**Constraints:**

* `1 <= nums.length <= 10`
* `-10 <= nums[i] <= 10`

### Solution

#### Approach #0

```go
func subsetsWithDup(nums []int) (ans [][]int) {
    sort.Ints(nums)
    n := len(nums)
outer:
    for p := 0; p < 1<<n; p++ {
        var a []int
        for i, num := range nums {

            if p>>i&1 > 0 {
                if i > 0 && p>>(i-1)&1 == 0 && nums[i-1] == num {
                    continue outer
                }
                a = append(a, num)
            }

        }
        ans = append(ans, append([]int(nil), a...))
    }
    return
}
```

#### Approach #1

```go
func subsetsWithDup(nums []int) (ans [][]int) {
    sort.Ints(nums)
    n := len(nums)
    var tmp []int
    var dfs func(bool, int)
    dfs = func(choosePre bool, cur int) {
        if cur == n {
            ans = append(ans, append([]int(nil), tmp...))
            return
        }
        dfs(false, cur+1)
        if !choosePre && cur > 0 && nums[cur-1] == nums[cur] {
            return
        }
        tmp = append(tmp, nums[cur])
        dfs(true, cur+1)
        tmp = tmp[:len(tmp)-1]
    }
    dfs(false, 0)
    return
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://a.b.cr/dictionary/algorithm/diary/2022/06/2022-06-05.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.