全排列-回溯

Posted 2022-03-12 nevergiveup0

class Solution 
    public void back(int n,ArrayList<Integer> nums,List<List<Integer>> output,int first)
        if(first==n)output.add(new ArrayList<Integer>(nums));
        for(int i=first;i<n;i++)
            Collections.swap(nums,first,i);
            back(n,nums,output,first+1);
            Collections.swap(nums,i,first);
          
    
    public List<List<Integer>> permute(int[] nums) 
        int n=nums.length;
        List<List<Integer>> output=new ArrayList();
        ArrayList<Integer> nums2=new ArrayList<Integer>();
        for(int num:nums)
            nums2.add(num);
        
        back(n,nums2,output,0);
    return output;