Permutations II

Description:

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

For example,
[1,1,2] have the following unique permutations:
[1,1,2], [1,2,1], and [2,1,1].

Solution:

class Solution {
public:
vector<vector> permuteUnique(vector& nums) {
sort(begin(nums), end(nums));
vector<vector> rc;
permute(rc, nums, 0);
return rc;
}

private:
void permute(vector<vector>& result, vector nums, int k) {
auto sz = (int)nums.size();
if (k >= sz-1) {
result.push_back(nums);
return;
}
permute(result, nums, k+1);
for (int i = k+1; i < sz; ++i) {
if (nums[i] != nums[k]) {
swap(nums[k], nums[i]);
permute(result, nums, k+1);
}
}
}
};

class Solution {
public:
vector<vector> permuteUnique(vector& nums) {
sort(begin(nums), end(nums));
vector<vector> rc;
do {
rc.push_back(nums);
} while (next_permutation(begin(nums), end(nums)));
return rc;
}
};