Sequence 系列

经典题目

Try to start from the lowest number of a streak, then test y = x + 1, x + 2, ..., until y is not in the set. Then the length would be simply y - x.

128 Longest Consecutive Sequence

public int longestConsecutive(int[] nums) {
    Set<Integer> set = new HashSet<>();
    for (int num : nums) {
        set.add(num);
    }
    int longest = 0;
    for (int num : nums) {
        if (!set.contains(num - 1)) {
            int curLength = 1;
            int curNum = num;
            while (set.contains(num + 1)) {
                curLength += 1;
                num += 1;
            }
            longest = Math.max(longest, curLength);
        }
    }
    return longest;
}