LongestConsecutive

//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.HashSet;


public class LongestConsecutive {


public static void main(String[] args) {
// TODO 自动生成的方法存根

}
public static int longestConsecutive(int[] num) {
if(num.length==0){
return 0;
}
int max=1;
HashSet set=new HashSet();
for(int e:num){
set.add(e);
}
 
for(int e:num){


int left=e - 1;
int right=e + 1;
int count=1;
while(set.contains(left)){
count++;
set.remove(left);
left--;
}
while(set.contains(right)){
count++;
set.remove(right);
right++;

}
max=Math.max(max, count);
}
return max;
}


}