Given a binary array, find the maximum length of a contiguous subarray with equal number of 0 and 1.
Example 1:
Input: [0,1]
Output: 2
Explanation: [0, 1] is the longest contiguous subarray with equal number of 0 and 1.
Example 2:
```txt
Input: [0,1,0]
Output: 2
Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.
Note: The length of the given binary array will not exceed 50,000.
A picture inside solution secture helps a lot. Solution
class Solution {
public int findMaxLength(int[] nums) {
Map<Integer, Integer> firstOc = new HashMap<>();
firstOc.put(0, -1);
int maxLength = 0;
int counter = 0;
for (int i = 0; i < nums.length; i++) {
counter+= (nums[i] == 0) ? -1: 1;
Integer it = firstOc.get(counter);
if (it != null) {
maxLength = Math.max(maxLength, i - it);
} else {
firstOc.put(counter, i);
}
}
return maxLength;
}
}