LeetCode: Contiguous Array

LeetCode: Contiguous Array

Given a binary array, find the maximum length of a contiguous subarray with equal number of 0 and 1.

Example 1:

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Input: [0,1]
Output: 2
Explanation: [0, 1] is the longest contiguous subarray with equal number of 0 and 1.

Example 2:

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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.

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public class Solution {
    public int findMaxLength(int[] nums) {
        if (nums == null || nums.length < 2) return 0;

        int sum = 0;
        int result = 0;
        Map<Integer, Integer> dict = new HashMap<>();
        dict.put(0, -1);
        for (int i = 0; i < nums.length; i++) {
            sum += (nums[i] << 1) - 1;
            if (dict.containsKey(sum)) {
                result = Math.max(result, i - dict.get(sum));
            } else {
                dict.put(sum, i);
            }
        }
        return result;
    }
}