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1573. Number of Ways to Split a String (Medium)

Given a binary string s, you can split s into 3 non-empty strings s1, s2, and s3 where s1 + s2 + s3 = s.

Return the number of ways s can be split such that the number of ones is the same in s1, s2, and s3. Since the answer may be too large, return it modulo 109 + 7.

 

Example 1:

Input: s = "10101"
Output: 4
Explanation: There are four ways to split s in 3 parts where each part contain the same number of letters '1'.
"1|010|1"
"1|01|01"
"10|10|1"
"10|1|01"

Example 2:

Input: s = "1001"
Output: 0

Example 3:

Input: s = "0000"
Output: 3
Explanation: There are three ways to split s in 3 parts.
"0|0|00"
"0|00|0"
"00|0|0"

 

Constraints:

• 3 <= s.length <= 105
• s[i] is either '0' or '1'.

Related Topics

[Math] [String]

Similar Questions

1. Split Array with Equal Sum (Hard)

Hints

Hint 1

There is no way if the sum (number of '1's) is not divisible by the number of splits. So sum%3 should be 0.

Hint 2

Preffix s1 , and suffix s3 should have sum/3 characters '1'.

Hint 3

Follow up: Can you generalize the problem with numbers between [-10^9, 10^9] such the sum between subarrays s1, s2, s3 are the same?