给定一个无序数组arr，其中元素可正、可负、可0。求arr所有子数组中正数与负数个数相等的最长子数组的长度。

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static Scanner sc = new Scanner(System.in);

    /*
5
1 -2 1 1 1

2
     */
    public static void main(String[] args) {

        int n = sc.nextInt();
        int[] arr = new int[n];
        for(int i=0;i<n;i++){
            int tmp = sc.nextInt();
            if(tmp < 0){
                tmp = -1;
            }
            if(tmp > 0){
                tmp = 1;
            }
            arr[i] = tmp;
        }
        int k = 0;
        int maxLen = 0;
        int sum = 0; // 0 位置到 i位置的sum
        Map<Integer, Integer> sumPosMap = new HashMap<>(32); // sum 第一次出现的 i
        sumPosMap.put(0, -1);
        for(int i = 0; i < n; i++){
            sum += arr[i];
            if(sumPosMap.containsKey(sum-k)){
                int firstPos = sumPosMap.get(sum - k);
                if(i - firstPos > maxLen){
                    maxLen = i - firstPos;
                }
            }
            if(!sumPosMap.containsKey(sum)){
                sumPosMap.put(sum, i);
            }
        }
        System.out.println(maxLen);
    }

}

import java.util.Scanner;

public class Main {

    public static Scanner sc = new Scanner(System.in);

    /*
5
1 -2 1 1 1

2
     */
    public static void main(String[] args) {

        int n = sc.nextInt();
        int[] arr = new int[n];
        // sum[j] - sums[i] : 表示区间：[i, j-1]
        int[] sums = new int[n + 1];
        for(int i=0;i<n;i++){
            int tmp = sc.nextInt();
            if(tmp < 0){
                tmp = -1;
            }
            if(tmp > 0){
                tmp = 1;
            }
            arr[i] = tmp;
            if(i == 0){
                sums[i + 1] = arr[i];
            }else {
                sums[i + 1] = sums[i] + arr[i];
            }
        }
        int k = 0;
        int ans = 0;
        for(int i=0;i<n;i++){
            for(int j=i;j<n;j++){
                int tmp;
                int len = j - i + 1;
                if(len <= ans){
                    continue;
                }
                if(j == i){
                    tmp = arr[i];
                }else {
                    tmp = sums[j + 1] - sums[i];
                }
                if(tmp == k){
                    ans = Math.max(ans, len);
                }
            }
            if(n - i < ans){
                break;
            }
        }
        System.out.println(ans);
    }

}