Longest Consecutive Sequence

最新推荐文章于 2025-03-19 23:17:40 发布

转载最新推荐文章于 2025-03-19 23:17:40 发布 · 248 阅读

leetcode 同时被 2 个专栏收录

174 篇文章

订阅专栏

fast

57 篇文章

订阅专栏

本文介绍了一种寻找整数数组中最长连续元素序列的算法。通过使用哈希表，该算法能在O(n)的时间复杂度内找到最长连续序列的长度。示例中给出了具体实现过程。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.

For example,
Given [100, 4, 200, 1, 3, 2],
The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4.

Your algorithm should run in O(n) complexity.

public int longestConsecutive(int[] num) {
        HashMap<Integer, Integer> hs = new HashMap<Integer, Integer>();
        for(int i: num){
            hs.put(i, 0);
        }
        int maxl = 1;
        for(int i: num){
            if (hs.get(i) == 1) continue;

            int tmp = i;
            int current_max = 1;
            while(hs.containsKey(tmp+1)){
                current_max ++;
                tmp ++;
                hs.put(tmp, 1);
            }

            tmp = i;
            while(hs.containsKey(tmp-1)){
                current_max ++;
                tmp --;
                hs.put(tmp, 1);
            }

            maxl = Math.max(current_max, maxl);
        }

        return maxl;
    }