import java.util.HashSet;
import java.util.Set;
public class longstack {
public static int longestConsecutive(int[] nums){
Set num_set = new HashSet();
for(int num : nums){
num_set.add(num);
}
int longstack;
int currentnumber;
int maxlongstack=0;
// System.out.println(555);
for(int num : num_set){
System.out.println(num);
if(!num_set.contains(num-1)){//确定当å‰æ˜¯æœ€å°çš„æ•°;
longstack=1;
currentnumber=num;
// System.out.println(currentnumber);
while(num_set.contains(currentnumber+1)){
longstack+=1;
currentnumber+=1;
}
maxlongstack=Math.max(longstack,maxlongstack);
}
//o(n) times;
// traversal the array
//hashset can reduce o(times) to 1;
}
return maxlongstack;
}
public static void main(String[] args){
int[] y= new int[]{1,2,4,6,3};
int t=longstack.longestConsecutive(y);
System.out.println(t);
}
}