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].

思路：

同Permutations。

代码：

    vector<vector<int> > permuteUnique(vector<int> &num) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        vector<vector<int> > result;
        result.clear();
        int len = num.size();
        int i, j;
        if(len == 0)
            return result;
        sort(num.begin(), num.end());
        result.push_back(num);
        while(true){
            vector<int> tmp = result[result.size()-1];
            i = len-1;
            while(i > 0 && tmp[i] <= tmp[i-1]){
                i--;
            }
            if(i == 0)
                break;
            i--;
            j = len-1;
            while(tmp[j] <= tmp[i]){
                j--;
            }
            int t = tmp[i];
            tmp[i] = tmp[j];
            tmp[j] = t;
            i++;
            j = len-1;
            while(i < j){
                t = tmp[i];
                tmp[i] = tmp[j];
                tmp[j] = t;
                i++;
                j--;
            }
            result.push_back(tmp);
        }
        return result;
    }