Longest Consecutive Sequence

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本文介绍了一个用于寻找整数数组中最长连续元素序列的算法。该算法通过排序后遍历数组来实现，能在O(n log n)时间内找到最长连续序列的长度，并提供了具体实现代码及示例。

问题来源：https://leetcode.com/problems/longest-consecutive-sequence/

import java.util.Arrays;

/**
 * 
 * <p>
 * ClassName LongestConsecutiveSequence
 * </p>
 * <p>
 * Description Given an unsorted array of integers, find the length of the longest consecutive(连贯的；连续不断的) 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.
 * </p>
 * 
 * @author TKPad wangx89@126.com
 *         <p>
 *         Date 2015年3月20日 下午2:56:57
 *         </p>
 * @version V1.0.0
 *
 */
public class LongestConsecutiveSequence {
    public int longestConsecutive(int[] num) {
        int maxLength = 1;
        if (num == null || num.length <= 1) {
            return num.length;
        }
        Arrays.sort(num);
        int count = 1;
        for (int i = 1; i < num.length; i++) {
            if (1 == num[i] - num[i - 1]) {
                count++;
                if (count > maxLength) {
                    maxLength = count;
                }
            } else if (num[i] == num[i - 1]) {// 如果相等，计数器不变，maxLength不更新
                continue;
            } else {
                count = 1;
            }
        }
        return maxLength;
    }

    public static void main(String[] args) {
        // int longestConsecutive = new LongestConsecutiveSequence().longestConsecutive(new int[] { 100, 4, 200, 1, 3, 2 });
        // int longestConsecutive = new LongestConsecutiveSequence().longestConsecutive(new int[] { 100});
        // int longestConsecutive = new LongestConsecutiveSequence().longestConsecutive(new int[] {});
        int longestConsecutive = new LongestConsecutiveSequence().longestConsecutive(new int[] { 1, 2, 0, 1 });
        System.out.println(longestConsecutive);
    }
}