题目：

题解：

class Solution {public int findMaxLength(int[] nums) {int maxLength = 0;Map<Integer, Integer> map = new HashMap<Integer, Integer>();int counter = 0;map.put(counter, -1);int n = nums.length;for (int i = 0; i < n; i++) {int num = nums[i];if (num == 1) {counter++;} else {counter--;}if (map.containsKey(counter)) {int prevIndex = map.get(counter);maxLength = Math.max(maxLength, i - prevIndex);} else {map.put(counter, i);}}return maxLength;}
}