2022-06-05

78. 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

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

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

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

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

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
}