LeetCode Permutations

Given a collection of distinct 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],
[3,2,1]
]

思路：通过回溯来实现，采用了递归

代码如下:

class Solution {
public:
void swap(vector<int>& nums,int i,int j)
{
if(i!=j)
{
nums[i] ^= nums[j];
nums[j] ^= nums[i];
nums[i] ^= nums[j];
}
}
void accumlate(vector<vector<int>>& res,vector<int>& nums,int begin)
{
if(begin == nums.size())
{
res.push_back(nums);
return;
}
for(int i = begin;i<nums.size();i++)
{
swap(nums,begin,i);
accumlate(res,nums,begin+1);
swap(nums,begin,i);
}
}
vector<vector<int>> permute(vector<int>& nums) {
vector<vector<int>> res;
accumlate(res,nums,0);
return res;
}
};