#927

Three Equal Parts

hard · verified · 41.3% accepted · 855 likes · top 22%

array · math

Description

You are given an array arr which consists of only zeros and ones, divide the array into three non-empty parts such that all of these parts represent the same binary value.

If it is possible, return any [i, j] with i + 1 < j, such that:

- arr[0], arr[1], ..., arr[i] is the first part,

- arr[i + 1], arr[i + 2], ..., arr[j - 1] is the second part, and

- arr[j], arr[j + 1], ..., arr[arr.length - 1] is the third part.

- All three parts have equal binary values.

If it is not possible, return [-1, -1].

Note that the entire part is used when considering what binary value it represents. For example, [1,1,0] represents 6 in decimal, not 3. Also, leading zeros are allowed, so [0,1,1] and [1,1] represent the same value.

Example 1:

Input: arr = [1,0,1,0,1]
Output: [0,3]

Example 2:

Input: arr = [1,1,0,1,1]
Output: [-1,-1]

Example 3:

Input: arr = [1,1,0,0,1]
Output: [0,2]

Solution