LeetCode Longest Consecutive Sequence

Use HashSet
public int longestConsecutive(int[] nums) {
        HashSet<Integer> set = new HashSet<Integer>();
for (int i : nums) {
set.add(i);
}
int max=0;
for (int i:nums) {
int cnt = 1;
set.remove(i);
int temp = i;
while (set.contains(temp-1)) {
set.remove(temp-1);
temp--;
cnt++;
}
temp=i;
while (set.contains(temp+1)) {
set.remove(temp+1);
temp++;
cnt++;
}
max = Math.max(max, cnt);
}
return max;
}

Use HashMap
This is from Jiaxin's leetcode
http://shanjiaxin.blogspot.com/2014/04/longest-consecutive-sequence-leetcode.html

public int longestConsecutive(int[] num) {


  if (num == null || num.length == 0) {


   return 0;


  }


  


  HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();


  for (int value : num) {


   map.put(value, 0);


  }


  


  int maxLength = 1;


  for (int i : num) {


   if (map.get(i) == 1) {


    continue;


   }


   


   // Search Increasing sequence for current element(right side)


   int temp = i;


   int current_max = 1;


   while (map.containsKey(temp + 1)) {


    current_max++;


    temp++;


    map.put(temp, 1);


   }


   


   // Search Descending sequence for current element(left side)


   temp = i;


   while (map.containsKey(temp - 1)) {


    current_max++;


    temp --;


    map.put(temp, 1);


   }


   


   maxLength = Math.max(current_max, maxLength);


  }


  


  return maxLength;


    }