leetcode546_leetcode 5

class Solution { 

public:
vector<vector<int>> permute(vector<int>& nums) { 

vector<vector<int>> ans;
vector<int> origin = nums;
ans.push_back(origin);
nextPermutation(nums);
while (origin != nums) { 

ans.push_back(nums);
nextPermutation(nums);
}
return ans;
}
void nextPermutation(vector<int>& nums) { 

if (nums.size() == 0) return;
int i = nums.size() - 2, j;
while(i >= 0 && nums[i] >=n ums[i+1]) i--;
if(i >= 0) { 
  
j = i + 1;  
while(j <n ums.size() && nums[j] > nums[i]) j++;  
j--;
swap(nums[i], nums[j]);
}
i++; j = nums.size() - 1;
while (i < j) { 

swap(nums[i], nums[j]);
i++; j--;
}
}
};