add 660

Author: fishercoder1534

README.md

@@ -22,6 +22,7 @@ Your ideas/fixes/algorithms are more than welcome!
 
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|660|[Remove 9](https://leetcode.com/problems/remove-9/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_660.java) | O(n) | O(1) | Hard | Math
 |659|[Split Array into Consecutive Subsequences](https://leetcode.com/problems/split-array-into-consecutive-subsequences/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_659.java) | O(n) | O(n) | Medium | HashMap
 |658|[Find K Closest Elements](https://leetcode.com/problems/find-k-closest-elements/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_658.java) | O(n) | O(1) | Medium |
 |657|[Judge Route Circle](https://leetcode.com/problems/judge-route-circle/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_657.java) | O(n) | O(1) | Easy | 

src/main/java/com/fishercoder/solutions/_660.java

@@ -0,0 +1,38 @@
+package com.fishercoder.solutions;
+
+/**
+ * 660. Remove 9
+ *
+ * Start from integer 1, remove any integer that contains 9 such as 9, 19, 29...
+
+ So now, you will have a new integer sequence: 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, ...
+
+ Given a positive integer n, you need to return the n-th integer after removing. Note that 1 will be the first integer.
+
+ Example 1:
+ Input: 9
+ Output: 10
+
+ Hint: n will not exceed 9 x 10^8.
+ */
+public class _660 {
+
+    public static class Solution1 {
+        public int newInteger(int n) {
+            return Integer.parseInt(Integer.toString(n, 9));
+        }
+    }
+
+    public static class Solution2 {
+        public int newInteger(int n) {
+            int result = 0;
+            int base = 1;
+            while (n > 0) {
+                result += n % 9 * base;
+                n /= 9;
+                base *= 10;
+            }
+            return result;
+        }
+    }
+}