回溯Leetcode 47 Permutations II

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Leetcode 47

Permutations II

• Problem Description：
  经典回溯问题：重复数字的全排列
  具体的题目信息：
  https://leetcode.com/problems/permutations-ii/description/
• Example:
  
• Solution:

class Solution {
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>> res;
        if (nums.size() == 0) return res;
        vector<bool> used(nums.size(), false);
        vector<int> temp;
        sort(nums.begin(), nums.end());
        permutation(nums, used, res, temp);
        return res;
    }
    void permutation(vector<int>& nums, vector<bool>& used, vector<vector<int>>& res, vector<int>& temp) {
        if (temp.size() == nums.size()) {
            res.push_back(temp);
            return ;
        } else {
            for (int i = 0; i < nums.size(); i++) {
                if (used[i] ||(i>0&&nums[i] == nums[i-1]&&!used[i-1]))
                    continue;
                used[i] = true;
                temp.push_back(nums[i]);
                permutation(nums, used, res, temp);
                temp.erase(temp.begin()+temp.size()-1);
                used[i] = false;
            }
        }
    }
};