README.md

842. Split Array into Fibonacci Sequence

You are given a string of digits num, such as "123456579". We can split it into a Fibonacci-like sequence [123, 456, 579].

Formally, a Fibonacci-like sequence is a list f of non-negative integers such that:

• 0 <= f[i] < 231, (that is, each integer fits in a 32-bit signed integer type),
• f.length >= 3, and
• f[i] + f[i + 1] == f[i + 2] for all 0 <= i < f.length - 2.

Note that when splitting the string into pieces, each piece must not have extra leading zeroes, except if the piece is the number 0 itself.

Return any Fibonacci-like sequence split from num, or return [] if it cannot be done.

Example 1:

Input: num = "1101111"
Output: [11,0,11,11]
Explanation: The output [110, 1, 111] would also be accepted.

Example 2:

Input: num = "112358130"
Output: []
Explanation: The task is impossible.

Example 3:

Input: num = "0123"
Output: []
Explanation: Leading zeroes are not allowed, so "01", "2", "3" is not valid.

Constraints:

• 1 <= num.length <= 200
• num contains only digits.

Solutions (Python)

1. Solution

class Solution:
    def splitIntoFibonacci(self, num: str) -> List[int]:
        for i in range(1, min(11, (len(num) + 1) // 2)):
            if i > 1 and num[0] == '0':
                break

            for j in range(i + 1, min(i + 11, len(num))):
                if j - i > 1 and num[i] == '0':
                    break

                seq = [int(num[:i]), int(num[i:j])]
                k = j

                while k < len(num):
                    size = len(str(seq[-2] + seq[-1]))
                    seq.append(int(num[k:k + size]))
                    k += size

                    if seq[-1] >= 2147483648 or seq[-3] + seq[-2] != seq[-1]:
                        seq = []
                        break

                if seq != []:
                    return seq

        return []