java 代码

import java.io.BufferedInputStream;
import java.util.Scanner;

import static java.lang.Math.max;

/**
 * 双指针算法
 * 求 最长了连续不重复子序列
 */
public class Main {

    private static final int N = 100010;
    private static int[] a = new int[N];//原始数组
    private static int[] b = new int[N];//记录每个数出现的次数
    public static void main(String[] args) {
        Scanner sc = new Scanner(new BufferedInputStream(System.in));
        int n = sc.nextInt();

        for (int i = 0; i < n; i++) a[i] = sc.nextInt();

        int res = 0;
        for (int i = 0, j = 0; j < n; j++) {
            b[a[j]]++;
            while (b[a[j]] > 1) {
                b[a[i]]--;
                i++;
            }
            res = max(res, j - i + 1);

        }
        System.out.println(res);

    }
}