386. Lexicographical Numbers

Author: zhaoguanchen

README.md

@@ -162,6 +162,7 @@ The project is divided into two parts: `structure` and `solution`.
 | 31   | [Next Permutation](https://leetcode.com/problems/next-permutation/) | Medium     | [NextPermutation.java](src/leetcode/solution/array/NextPermutation.java) | Find the first element that is greater than the previous element, then replace it with the greater and smallest element on the right side. |
 | 228  | [Summary Ranges](https://leetcode.com/problems/summary-ranges/) | Easy       | [SummaryRanges.java](src/leetcode/solution/array/SummaryRanges.java) | Two Pointer.                                                 |
 | 281  | [Zigzag Iterator](https://leetcode.com/problems/zigzag-iterator/) | Medium     | [ZigzagIterator.java](src/leetcode/solution/array/ZigzagIterator.java) | Two Pointer<br />Muti Pointer or Queue for the **Follow-Up** Question. |
+| 386  | [Lexicographical Numbers](https://leetcode.com/problems/lexicographical-numbers/) | Medium     | [LexicographicalNumbers.java](src/leetcode/solution/array/LexicographicalNumbers.java) | Recursion                                                    |
 | 412  | [Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)        | Easy       | [FizzBuzz.java](src/leetcode/solution/array/FizzBuzz.java)   | For loop. Calculate i%5 and i%3 separately.                  |
 | 456  | [132 Pattern](https://leetcode.com/problems/132-pattern/)    | Medium     | [OneThreeTwoPattern.java](src/leetcode/solution/array/OneThreeTwoPattern.java) | Using Array as a Stack                                       |
 | 768  | [Max Chunks To Make Sorted II](https://leetcode.com/problems/max-chunks-to-make-sorted-ii/) | Hard       | [MaxChunksToMakeSortedII.java](src/leetcode/solution/array/MaxChunksToMakeSortedII.java) | Iterate through the array, each time all elements to the left are smaller (or equal) to all elements to the right, there is a new chunk. |

src/leetcode/solution/array/LexicographicalNumbers.java

@@ -0,0 +1,49 @@
+package leetcode.solution.array;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 386. Lexicographical Numbers
+ */
+public class LexicographicalNumbers {
+
+    public static void main(String[] args) {
+        int n = 13;
+        LexicographicalNumbersSolution solution = new LexicographicalNumbersSolution();
+        List<Integer> ans = solution.lexicalOrder(n);
+        System.out.println(ans);
+    }
+
+}
+
+class LexicographicalNumbersSolution {
+
+    List<Integer> ans;
+
+    int n;
+
+    public List<Integer> lexicalOrder(int n) {
+        ans = new ArrayList<>();
+        this.n = n;
+        create(0);
+        return ans;
+    }
+
+    private void create(int base) {
+        for (int i = 0; i < 10; i++) {
+            int next = base + i;
+            if (next > n) {
+                break;
+            }
+
+            if (next == 0) {
+                continue;
+            }
+
+            ans.add(next);
+            create(next * 10);
+        }
+
+    }
+}