Longest Subarray with Equal Number of 0's and 1's

You are given a binary string S consisting only of characters '0' and '1'. Your task is to find the length of the longest contiguous subarray that has an equal number of 0's and 1's.

Problem Statement:

Given a binary string S, determine the maximum length of a subarray (continuous segment) where the number of 0's is equal to the number of 1's. If no such subarray exists, output 0.

Example:

• For S = "1100011", the longest subarray with equal number of 0's and 1's has length 6.
• For S = "000000", there is no subarray with equal number of 0's and 1's, so the output is 0.

The solution should be efficient and able to handle large input sizes.

Hint:

You may use a hashmap (or dictionary) to store the first occurrence of a particular running count difference. Use the technique of prefix sum where you increment the count for '1' and decrement for '0'.

inputFormat

The input consists of a single line containing the binary string S (only characters '0' and '1'). Input is provided from stdin.

outputFormat

Output a single integer which is the length of the longest contiguous subarray with equal number of 0's and 1's. The result should be printed to stdout.

## sample

1100011

6