44. Longest Consecutive Sequence-最长连续序列

题目描述：


解析：hashSet作记录 从左往右搜 从右往左搜

class Solution {
    public int longestConsecutive(int[] nums) {
        HashSet<Integer> set = new HashSet<>();
        int longest = 0; //记录长度
        for (int num : nums) {
            set.add(num);
        }
        for (int num : nums) {
            //从左往右搜 例如100，搜索101，102，103....
            int currNum = num;
            int currLong = 1;
            while (set.remove(currNum + 1)) currNum++;
            currLong += currNum - num;
            //从右往左搜 例如100，搜索99，98，97....
            currNum = num;
            while (set.remove(currNum - 1)) currNum--;
            currLong += num - currNum;
            longest = Math.max(longest, currLong);
        }
        return longest;
    }
}