【LeetCode】#128最长连续序列(Longest Consecutive Sequence)

【LeetCode】#128最长连续序列(Longest Consecutive Sequence)

题目描述

给定一个未排序的整数数组，找出最长连续序列的长度。
要求算法的时间复杂度为 O(n)。

示例

输入: [100, 4, 200, 1, 3, 2]
输出: 4
解释: 最长连续序列是 [1, 2, 3, 4]。它的长度为 4。

Description

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
Your algorithm should run in O(n) complexity.

Example

Input: [100, 4, 200, 1, 3, 2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.

解法

class Solution {
    public int longestConsecutive(int[] nums) {
        if(nums.length==0){
            return 0;
        }
        Arrays.sort(nums);
        int x = nums[0];
        int sum = 1;
        int res = 0;
        for(int i=1; i<nums.length; i++){
            if(nums[i]==x){
                continue;
            }else if(nums[i]==++x){
                sum++;    
            }else{
                res = Math.max(res, sum);
                sum = 1;
                x = nums[i];
            }
        }
        res = Math.max(res, sum);
        return res;
    }
}