Count the number of contiguous subarrays where the ratio of even numbers to odd numbers satisfies a given condition.
Problem
Given an integer array nums, count how many contiguous subarrays satisfy the condition described by the problem’s even/odd ratio definition.
This problem is centered on turning a subarray condition into a running-state counting problem. You should look for a way to evaluate many subarrays efficiently instead of checking each one independently.
Notes
- A subarray must be contiguous.
- The condition depends only on the parity counts inside the subarray.
- The array may contain positive, negative, or zero values; parity is determined in the usual way.
Goal
Return the total number of valid subarrays.
Input Format
- An integer array
nums. - The exact ratio threshold/condition is implied by the problem statement and the title.
Output Format
- Return an integer representing the number of contiguous subarrays that satisfy the condition.
Constraints
1 <= nums.length.- Values fit in standard 32-bit signed integers.
- Expected solution should be better than for typical interview constraints.
Example 1
Input
nums = [1, 2, 3, 4]
Output
4
Explanation
Illustrative example: count all contiguous subarrays that satisfy the even/odd ratio rule.
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