Create 066_Plus_One.java (qiyuangong#33)

* Create 066_Plus_One.java, by @hvsalesforce

Author: hvsalesforce

java/066_Plus_One.java

@@ -0,0 +1,23 @@
+class Solution {
+    public int[] plusOne(int[] digits) {
+            return addToDigit(digits, digits.length - 1);
+        }
+
+        private int[] addToDigit(int[] digits, int index) {
+            if (index == -1) {
+                int[] newDigits = new int[digits.length + 1];
+                newDigits[0] = 1;
+                for (int i = 0; i < digits.length; i++) {
+                    newDigits[i + 1] = digits[i];
+                }
+                return newDigits;
+            }
+            if (digits[index] == 9) {
+                digits[index] = 0;
+                return addToDigit(digits, index - 1);
+            } else {
+                digits[index]++;
+                return digits;
+            }
+        }
+}