- Difficulty: Medium
- Tags: LeetCode, Medium, Hash Table, Math, String, Prefix Sum, leetcode-2489, O(n), 🔒, Freq Table
Problem
You are given a binary string s
, and two integers num1
and num2
. num1
and num2
are coprime numbers.
A ratio substring is a substring of s where the ratio between the number of 0
's and the number of 1
's in the substring is exactly num1 : num2
.
- For example, if
num1 = 2
andnum2 = 3
, then"01011"
and"1110000111"
are ratio substrings, while"11000"
is not.
Return the number of non-empty ratio substrings of s
.
Note that:
- A substring is a contiguous sequence of characters within a string.
- Two values
x
andy
are coprime ifgcd(x, y) == 1
wheregcd(x, y)
is the greatest common divisor ofx
andy
.
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Example 1:
Input: s = "0110011", num1 = 1, num2 = 2 Output: 4 Explanation: There exist 4 non-empty ratio substrings. - The substring s[0..2]: "0110011". It contains one 0 and two 1's. The ratio is 1 : 2. - The substring s[1..4]: "0110011". It contains one 0 and two 1's. The ratio is 1 : 2. - The substring s[4..6]: "0110011". It contains one 0 and two 1's. The ratio is 1 : 2. - The substring s[1..6]: "0110011". It contains two 0's and four 1's. The ratio is 2 : 4 == 1 : 2. It can be shown that there are no more ratio substrings.
Example 2:
Input: s = "10101", num1 = 3, num2 = 1 Output: 0 Explanation: There is no ratio substrings of s. We return 0.
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Constraints:
1 <= s.length <= 105
1 <= num1, num2 <= s.length
num1
andnum2
are coprime integers.