medium
source: https://leetcode.com/problems/subsets-ii/
C/C++ Solution to LeetCode problem 90. Subsets II.
Problem
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.
Examples
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
This is very similar to problem 78, we will solve it using backtracking.
- To prevent duplicates, we first sort the array of numbers, and when adding them to the current subset, we will skip the repeated numbers.
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class Solution {
private:
vector<vector<int>> powerset;
void generateSets(vector<int>& nums, vector<int>& sol, int index) {
powerset.push_back(sol);
for (int i=index; i<nums.size(); i++) {
if (i > index && nums[i] == nums[i-1])
continue;
sol.push_back(nums[i]);
generateSets(nums, sol, i+1);
sol.pop_back();
}
}
public:
vector<vector<int>> subsetsWithDup(vector<int>& nums) {
vector<int> sol;
sort(nums.begin(), nums.end());
generateSets(nums, sol, 0);
return powerset;
}
};