题解 | #牛群排列组合#

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param nums int整型vector 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > cow_permutation(vector<int>& nums) {
        // write code here
        int n = nums.size();
        set<vector<int>> res;
        recurse(nums,0,res);
        vector<vector<int>> ret(res.rbegin(),res.rend());
        return ret;
    }
    void recurse(vector<int> & nums, int start, set<vector<int>> &res){
        if(start == nums.size()-1){
            res.insert(nums);
            return;
        }
        for(int i = start;i<nums.size();i++){
            swap(nums[start],nums[i]);
            recurse(nums, start + 1,res);
            swap(nums[start],nums[i]);
        }
    }
};