Note: 1. Remember to intial (0, -1) since this kind of problems need a starting point.

class Solution {    public int findMaxLength(int[] nums) {        if (nums.length < 2) {            return 0;        }                 for (int i = 0; i < nums.length; i++) {            if (nums[i] == 0) {                nums[i] = -1;            }        }                Map
     
       sumMap = new HashMap<>();        sumMap.put(0, -1);        int sum = 0;        int result = 0;        for (int i = 0; i < nums.length; i++) {            sum += nums[i];            if (!sumMap.containsKey(sum)) {                sumMap.put(sum, i);            } else {                result = Math.max(result, i - sumMap.get(sum));            }        }        return result;    }}