ArrayPrefix SumHash Map
Given a binary array of 0s and 1s, find the length of the longest contiguous subarray that contains an equal number of 0s and 1s.
Input
Line 1: n. Line 2: n values, each 0 or 1.
Output
Print the length of the longest balanced subarray (0 if none exists).
Constraints
1 <= n <= 10^5
Example 1
Input
2 0 1
Output
2
The whole array has one 0 and one 1.
Example 2
Input
3 0 1 0
Output
2
The first two (or last two) elements are balanced.