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76 lines
1.7 KiB
Markdown
Executable File
76 lines
1.7 KiB
Markdown
Executable File
# [90. Subsets II](https://leetcode.com/problems/subsets-ii/)
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## 题目
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Given a collection of integers that might contain duplicates, ***nums***, return all possible subsets (the power set).
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**Note**: The solution set must not contain duplicate subsets.
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**Example**:
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Input: [1,2,2]
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Output:
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[
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[2],
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[1],
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[1,2,2],
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[2,2],
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[1,2],
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[]
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]
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## 题目大意
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给定一个可能包含重复元素的整数数组 nums，返回该数组所有可能的子集（幂集）。说明：解集不能包含重复的子集。
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## 解题思路
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- 这一题是第 78 题的加强版，比第 78 题多了一个条件，数组中的数字会出现重复。
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- 解题方法依旧是 DFS，需要在回溯的过程中加上一些判断。
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- 这一题和第 78 题，第 491 题类似，可以一起解答和复习。
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## 代码
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```go
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package leetcode
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import (
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"fmt"
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"sort"
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)
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func subsetsWithDup(nums []int) [][]int {
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c, res := []int{}, [][]int{}
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sort.Ints(nums) // 这里是去重的关键逻辑
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for k := 0; k <= len(nums); k++ {
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generateSubsetsWithDup(nums, k, 0, c, &res)
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}
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return res
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}
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func generateSubsetsWithDup(nums []int, k, start int, c []int, res *[][]int) {
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if len(c) == k {
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b := make([]int, len(c))
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copy(b, c)
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*res = append(*res, b)
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return
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}
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// i will at most be n - (k - c.size()) + 1
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for i := start; i < len(nums)-(k-len(c))+1; i++ {
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fmt.Printf("i = %v start = %v c = %v\n", i, start, c)
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if i > start && nums[i] == nums[i-1] { // 这里是去重的关键逻辑,本次不取重复数字，下次循环可能会取重复数字
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continue
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}
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c = append(c, nums[i])
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generateSubsetsWithDup(nums, k, i+1, c, res)
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c = c[:len(c)-1]
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}
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return
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}
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``` |