Sawtooth Subsequence

Given an array of integers, count the number of contiguous subsequences of alternating parity numbers, including length 1.

First approach (incorrect): array memo

Init memo arr
Traverse integer array [i... arr.length]
	if not matching parity
		memo[i] = memo[i - 1] + i + 1
	else:
		memo[i] = memo[i - 1] + 1
return memo[memo.length - 1]

Issue

Cannot increment memo[i] by i since it keeps increasing even when a subsequence is broken.

Fix

A separate pointer that resets to 1 whenever a contiguous subsequence is broken. Utilized to increment memo by the corresponding amount for its subsequence.

Optimization

Only using a prev pointer instead of an array since only last element is needed

VISA GCA