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diff --git a/‎leetcode-algorithms/src/main/java/com/stevesun/solutions/AdditiveNumber.java
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 |314|[Binary Tree Vertical Order Traversal](https://leetcode.com/problems/binary-tree-vertical-order-traversal/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/BinaryTreeVerticalOrderTraversal.java)| O(n)|O(n) | Medium| HashMap, BFS
 |311|[Sparse Matrix Multiplication](https://leetcode.com/problems/sparse-matrix-multiplication/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/SparseMatrixMultiplication.java)| O(m*n*l)|O(m*l)| Medium|
 |308|[Range Sum Query 2D - Mutable](https://leetcode.com/problems/range-sum-query-2d-mutable/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/RangeSumQuery2DMutable.java)| ? | ? | Hard| Tree
+|306|[Additive Number](https://leetcode.com/problems/additive-number/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/AdditiveNumber.java)| ? | ? | Medium|
 |305|[Number of Islands II](https://leetcode.com/problems/number-of-islands-ii/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/NumberofIslandsII.java)| ? | ? | Hard| Union Find
 |302|[Smallest Rectangle Enclosing Black Pixels](https://leetcode.com/problems/smallest-rectangle-enclosing-black-pixels/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/SmallestRectangleEnclosingBlackPixels.java)| ? | O(m*n) | Hard| DFS, BFS
 |301|[Remove Invalid Parentheses](https://leetcode.com/problems/remove-invalid-parentheses/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/RemoveInvalidParentheses.java)| ? | ? | Hard| BFS
 
@@ -0,0 +1,54 @@
+package com.stevesun.solutions;
+
+/**
+ * Additive number is a string whose digits can form additive sequence.
+
+ A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding two.
+
+ For example:
+ "112358" is an additive number because the digits can form an additive sequence: 1, 1, 2, 3, 5, 8.
+
+ 1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8
+ "199100199" is also an additive number, the additive sequence is: 1, 99, 100, 199.
+ 1 + 99 = 100, 99 + 100 = 199
+ Note: Numbers in the additive sequence cannot have leading zeros, so sequence 1, 2, 03 or 1, 02, 3 is invalid.
+
+ Given a string containing only digits '0'-'9', write a function to determine if it's an additive number.
+
+ Follow up:
+ How would you handle overflow for very large input integers?
+ */
+public class AdditiveNumber {
+
+    public boolean isAdditiveNumber(String num) {
+        if (num == null || num.length() < 3) {
+            return false;
+        }
+        int len = num.length();
+        for (int i = 1; i < len; i++) {
+            for (int j = i + 1; j < len; j++) {
+                int first = 0, second = i, third = j;
+                if (num.charAt(second) == '0' && third > second + 1){
+                    break;// This is the pruning part, for each iteration, if this condition
+                    // meets, returns false immediately
+                }
+                while (third < len) {
+                    Long result = Long.parseLong(num.substring(first, second))
+                            + Long.parseLong(num.substring(second, third));
+                    if (num.substring(third).startsWith((result.toString()))) {
+                        first = second;
+                        second = third;
+                        third += result.toString().length();
+                    } else {
+                        break;// This is another part of pruning! Cool!
+                    }
+                }
+                if(third == len){
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+}