525. Contiguous Array

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

Example 2:

Input: [0,1,0]Output: 2Explanation: [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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Links: https://leetcode.com/articles/contiguous-array/

Java Code:

public class Solution {    public int findMaxLength(int[] nums) {        if (null == nums || nums.length < 2) {            return 0;        }                int count = 0;        int maxLen = 0;        // sum, idex        Map<Integer, Integer> sumIdx = new HashMap<>();        sumIdx.put(0, -1);                for (int i = 0; i < nums.length; i++) {            count += (nums[i] == 0 ? -1 : 1);                        if (sumIdx.containsKey(count)) {                maxLen = Math.max(maxLen, i - sumIdx.get(count));            } else {                sumIdx.put(count, i);            }        }                return maxLen;    }}