LintCode(15) Permutations

Given a list of numbers, return all possible permutations.

Have you met this question in a real interview? 

Yes

Example

For nums = [1,2,3], the permutations are:

[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

Challenge

Do it without recursion.

没啥好说的。。。

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class Solution { public: /** * @param nums: A list of integers. * @return: A list of permutations. */ vector<vector<int> > permute(vector<int> nums) { // write your code here vector<vector<int>> result; vector<int> solution; if (nums.size()==0) return result; sort(nums.begin(), nums.end()); vector<bool> visited(nums.size(), false); dfs(nums,result,solution, visited); return result; } void dfs(vector<int>& nums, vector<vector<int>>& result, vector<int>& solution, vector<bool>& visited){ if (solution.size()==nums.size()){ result.push_back(solution); return; } for (int i=0; i<nums.size(); i++){ if (visited[i]) continue; visited[i]=true; solution.push_back(nums[i]); dfs(nums,result, solution, visited); visited[i]=false; solution.pop_back(); } } };