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Solution: Additive Number

Explore how to solve the additive number problem by employing backtracking to select the first two numbers and verify subsequent sums. Learn to handle constraints like leading zeros, and understand the solution's time and space complexity for robust coding interview preparation.

Statement

An additive number is a string whose digits can be partitioned into an additive sequence.

A valid additive sequence contains at least three numbers, where every number after the first two is equal to the sum of the two immediately preceding numbers.

Given a string, num, containing only digits, determine whether it represents an additive number. Return TRUE if a valid additive sequence can be formed from the digits of num, and FALSE otherwise.

Note: Numbers in the additive sequence cannot have leading zeros. For example, the sequences 1, 2, 03 and 1, 02, 3 are both invalid.

Constraints:

  • 11 \leq num.length ...