【Leetcode】46. Permutations(全排列)

46. Permutations(全排列)

题目：链接

代码一：

class Solution {
private:
    vector<vector<int>> rems;
public:
    vector<vector<int>> permute(vector<int>& nums) 
    {
        vector<int> out;
        vector<int> flag(nums.size(), 0);
        backtracking(nums, 0, out, flag);
        return rems;  
    }

    void backtracking(vector<int> &nums, int start, vector<int> &out, vector<int> &flag)
    {
        if(start == nums.size())
        {
            rems.push_back(out);
            return;
        }
        for(int i = 0; i < nums.size(); ++i)
            if(flag[i] == 0)
            {
                out.push_back(nums[i]);
                flag[i] = 1;
                backtracking(nums, start + 1, out, flag);
                out.pop_back();
                flag[i] = 0;
            }
    }
};

代码二：

 1 class Solution {
 2 private:
 3     vector<vector<int>> rems;
 4 public:
 5     vector<vector<int>> permute(vector<int>& nums) 
 6     {
 7         backtracking(nums, 0);
 8         return rems;  
 9     };
10 
11     void backtracking(vector<int> &nums, int end)
12     {
13         if(end == nums.size())
14         {
15             rems.push_back(nums);
16             return;
17         }
18         for(int i = end; i < nums.size(); ++i)
19         {
20             swap(nums[end], nums[i]);
21             backtracking(nums, end + 1);
22             swap(nums[end], nums[i]);
23         }
24     }
25 };