题目描述

blablabla

算法1

时间复杂度

O(n)

Java 代码

import java.util.*;

public class Main {
    public static void main (String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int [] a = new int[n];
        Map<Integer, Integer> map = new HashMap<>();

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

        int res = 0;
        for (int i = 0, j = 0; i < n; i++) {
            map.put(a[i], map.getOrDefault(a[i], 0) + 1); 
            while (map.get(a[i]) > 1) { 
                map.put(a[j], map.get(a[j]) - 1);
                j++;
            }
            res = Math.max(res, i - j + 1);
        }
        System.out.println(res);
    }
}