最长连续序列

// Solution in Java using Streams
// Approach: Similar to the above, but utilizing Java Streams for a more functional style.
// Time Complexity: O(n), Space Complexity: O(n)

import java.util.HashSet;
import java.util.Set;
import java.util.stream.IntStream;

public class StreamSolution {
    public int longestConsecutive(int[] nums) {
        if (nums.length == 0) return 0;
        Set<Integer> numSet = new HashSet<>();
        IntStream.of(nums).forEach(numSet::add);
        return numSet.stream().filter(num -> !numSet.contains(num - 1)).mapToInt(num -> {
            int currentNum = num;
            int currentStreak = 1;
            while (numSet.contains(currentNum + 1)) {
                currentNum += 1;
                currentStreak += 1;
            }
            return currentStreak;
        }).max().orElse(0);
    }
}