Leetcode-Longest Consecutive Sequence

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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.

Solution:

 1 public class Solution { 2     public int longestConsecutive(int[] num) { 3  4        Set<Integer> set = new HashSet<Integer>(); 5        for (int i=0;i<num.length;i++) set.add(num[i]);        6        int maxLen = 0; 7        int index = 0; 8        while (index<num.length){ 9            if (!set.contains(num[index])){10                index++;11                continue;12            }13 14            int len =0;15            int val = num[index];16            while (set.contains(val)){17                set.remove(val);18                len++;19                val--;20            }21            val = num[index]+1;22            while (set.contains(val)){23                set.remove(val);24                len++;25                val++;26            }27            if (maxLen<len) maxLen=len;28            index++;29        }30        31 32        return maxLen;33         34     }35 36 }

 

Leetcode-Longest Consecutive Sequence