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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.

Given a string containing only digits `'0'-'9'`

, write a function
to determine if it's an additive number.

**Note:** Numbers in the additive sequence **cannot** have leading zeros, so sequence
`1, 2, 03`

or `1, 02, 3`

is invalid.

**Example 1:**

Input:"112358"Output:trueExplanation: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

**Example 2:**

Input:"199100199"Output:trueExplanation:The additive sequence is: 1, 99, 100, 199. 1 + 99 = 100, 99 + 100 = 199

**Constraints:**

`num`

consists only of digits`'0'-'9'`

.`1 <= num.length <= 35`

**Follow up:**

How would you handle overflow for very large input integers?

All contents and pictures on this website come from the Internet and are updated regularly every week. They are for personal study and research only, and should not be used for commercial purposes. Thank you for your cooperation.