[LeetCode] Permutations II

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]

.

class Solution {
public:
vector<vector<int> > ans;
vector<int> v;
bool nums[100];
int len;
vector<vector<int> > permuteUnique(vector<int> &num) {
len = num.size();
memset(nums,false,sizeof(nums));
sort(num.begin(), num.end());
generate(num);
return ans;
}
void generate(vector<int> &num){
if(v.size() == len){
ans.push_back(v);
return;
}
for(int i = 0;i < len;i ++){
if(nums[i] == false){
if(i > 0 && num[i - 1] == num[i] && nums[i - 1] == false)
continue;
v.push_back(num[i]);
nums[i] = true;
generate(num);
v.pop_back();
nums[i] = false;
}
}
}
};