Algorithms—46.Permutations

思路：排列组合

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;
}
}