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] ]
public class Solution {
private List<List<Integer>> ans = new ArrayList<List<Integer>>();
public List<List<Integer>> permute(int[] nums) {
// Arrays.sort(nums);
// List<Integer> result = new ArrayList<Integer>();
if(nums.length<=0||nums == null)
return ans;
dfs(0,nums);
return ans;
}
void dfs(int start,int[] nums)
{
if(start == nums.length)
{
List<Integer> temp = new ArrayList<Integer>();
for(int i=0;i<nums.length;i++)
temp.add(nums[i]);
ans.add(temp);
}
else
{
for(int j=start;j<nums.length;j++)
{
int temp1 = nums[start];
nums[start] = nums[j];
nums[j] = temp1;
dfs(start+1,nums);
int temp2 = nums[start];
nums[start] = nums[j];
nums[j] = temp2;
}
}
}
}
