Solution.java

public class Solution {
    public List<List<Integer>> permute(int[] nums) {
		 List<List<Integer>> answerList=new ArrayList<List<Integer>>();
	        for (int i = 0; i < nums.length; i++) {
	        	int size=answerList.size();
				if (size==0) {
					for (int j = 0; j < nums.length; j++) {
						List<Integer> intList=new ArrayList<Integer>();
						intList.add(nums[j]);
						answerList.add(intList);
					}
				}else {
					for (int j = 0; j < size; j++) {
						List<Integer> intList=answerList.get(j);
						Map<Integer,String> map=new HashMap<Integer,String>();
						for (int l = 0; l <intList.size(); l++) {
							map.put(intList.get(l), "存在");
						}
						for (int k = 0; k < nums.length; k++) {
							if (map.get(nums[k])==null) {
								System.out.println("k="+k);
								List<Integer> newList=new ArrayList<Integer>();
								for (int l = 0; l < intList.size(); l++) {
									newList.add(intList.get(l));
								}
								newList.add(nums[k]);
								System.out.println();
								answerList.add(newList);
							}
						}
					}
					if (size!=answerList.size()) {
						for (int j = size-1; j >=0; j--) {
							answerList.remove(j);
						}
					}
				}
			}
		 
		 return answerList;
	    }
}