128. Longest Consecutive Sequence

csulfy

于 2016-12-07 21:16:22 发布

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分类专栏： LeetCode

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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，并提供了一个Java实现示例。该算法首先对数组进行排序，然后去除重复元素，最后通过遍历数组来计算最长连续序列的长度。

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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.

import java.util.ArrayList;
import java.util.Arrays;
public class Solution {
    public int longestConsecutive(int[] num) {
        Arrays.sort(num);
	        ArrayList<Integer> temp = new ArrayList<Integer>();
	        for(int i = 0;i<num.length;i++){
	        	if(!temp.contains(num[i])){
	        		temp.add(num[i]);
	        	}
	        }
	        int max = 1;
	        int count = 1;
	        for(int i = 0;i<temp.size();i++){
	        	if(i!=temp.size()-1&& temp.get(i+1)-temp.get(i) ==1){
	        		count = count +1 ;
	        	}
	        	else{
	        		count = 1;
	        	}
	        	if(count>=max){
	        		max = count;
	        	}
	        	
	        }
	        return max;
    }
}