[LeetCode]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]

.

题解：使用的是递归方法：

public class Solution {
    private List<List<Integer>> result = new ArrayList<List<Integer>>();
	
	public List<List<Integer>> permute(int[] nums) {
		generatePermute(nums,0,nums.length-1);
		return result;
	}
	public void generatePermute(int[] nums,int i,int n){
		if(i==n){
			putToList(nums);
		}else{
			
			for(int k=i; k<=n; k++){
				
				swap(nums, i, k);
				generatePermute(nums, i+1, n);
				swap(nums, i, k);
			}
		}
		
	}
	private static void swap(int [] nums,int i,int j){
		
		int tmp = nums[i];
		nums[i] = nums[j];
		nums[j] = tmp;
	}
	private void putToList(int[] nums) {
	 List<Integer> list = new ArrayList<Integer>();
	 for(int i:nums){
		 list.add(i);
	 }
	 result.add(list);
	}
}