#未排序数组中累加和为给定值的最长子数组系列问题补2#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int[] arr = new int[N];
        for (int i = 0; i < N; i++) {
            arr[i] = in.nextInt();
        }
        int len = getLength(arr);
        System.out.print(len);
    }

    private static int getLength(int[] arr) {
        if (arr == null) {
            return 0;
        }
        int N = arr.length;
        //key 正数个数与负数个数的差值, value index
        Map<Integer,Integer> map = new HashMap<>();
        map.put(0,-1);


        int Z = 0,F = 0;//1的个数，0的个数
        int res = 0;
        for (int i = 0; i < N; i++) {
            Z += arr[i] == 1 ? 1 : 0;
            F += arr[i] == 0 ? 1 : 0;
            int cha = Z - F;
            if (map.containsKey(cha)) {
                res = Math.max(res, i - map.get(cha));
            }else {
                map.put(cha,i);
            }
        }
        return res;
    }
}