添加0046.全排列新解法Java代码

problems/0046.全排列.md

@@ -183,6 +183,32 @@ class Solution {
     }
 }
 ```
+```java
+// 解法2：通过判断path中是否存在数字，排除已经选择的数字
+class Solution {
+    List<List<Integer>> result = new ArrayList<>();
+    LinkedList<Integer> path = new LinkedList<>();
+    public List<List<Integer>> permute(int[] nums) {
+        if (nums.length == 0) return result;
+        backtrack(nums, path);
+        return result;
+    }
+    public void backtrack(int[] nums, LinkedList<Integer> path) {
+        if (path.size() == nums.length) {
+            result.add(new ArrayList<>(path));
+        }
+        for (int i =0; i < nums.length; i++) {
+            // 如果path中已有，则跳过
+            if (path.contains(nums[i])) {
+                continue;
+            } 
+            path.add(nums[i]);
+            backtrack(nums, path);
+            path.removeLast();
+        }
+    }
+}
+```
 
 Python：
 ```python3