Permutations

最新推荐文章于 2024-12-15 00:58:33 发布

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最新推荐文章于 2024-12-15 00:58:33 发布

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Permutations

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

思路：运用递归求解，第一位和后面的每一位替换，递归到最后一位。

class Solution {
public:
    void permutation(vector<vector<int>> &ret, vector<int> &nums,int pStr,int pbegin)
    {
        if(pbegin == nums.size())
        ret.push_back(nums);
        else
        {
            for(int i = pbegin;i < nums.size();++i)
            {
                int tmp = nums[pbegin];
                nums[pbegin] = nums[i];
                nums[i] = tmp;
                permutation(ret,nums,pStr,pbegin+1);
                tmp = nums[pbegin];
                nums[pbegin] = nums[i];
                nums[i] = tmp;
            }
        }
    }
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> ret;
         if(0 == nums.size())
         return ret;
         permutation(ret,nums,0,0);
         return ret;
    }
};