leetcode[47]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:
bool isSwap(vector<int> &num, int i, int j)
{
int ii=i;
while(num[ii]!=num[j]&&ii<j)ii++;
if (ii==j)return true;
else return false;
}
void perm(vector<int> &num, int i, int N, vector<vector<int>> &res)
{
if(i==N)
res.push_back(num);
for (int j=i;j<N;j++)
{
if (!isSwap(num,i,j))continue;
swap(num[i],num[j]);
perm(num,i+1,N,res);
swap(num[j],num[i]);
}
}
vector<vector<int> > permuteUnique(vector<int> &num)
{
vector<vector<int> > res;
sort(num.begin(),num.end());
perm(num,0,num.size(),res);
return res;
}
};