# 最长连续序列

<p>给定一个未排序的整数数组 <code>nums</code> ，找出数字连续的最长序列（不要求序列元素在原数组中连续）的长度。</p>

<p>请你设计并实现时间复杂度为 <code>O(n)</code><em> </em>的算法解决此问题。</p>

<p> </p>

<p><strong>示例 1：</strong></p>

<pre>
<strong>输入：</strong>nums = [100,4,200,1,3,2]
<strong>输出：</strong>4
<strong>解释：</strong>最长数字连续序列是 <code>[1, 2, 3, 4]。它的长度为 4。</code></pre>

<p><strong>示例 2：</strong></p>

<pre>
<strong>输入：</strong>nums = [0,3,7,2,5,8,4,6,0,1]
<strong>输出：</strong>9
</pre>

<p> </p>

<p><strong>提示：</strong></p>

<ul>
	<li><code>0 <= nums.length <= 10<sup>5</sup></code></li>
	<li><code>-10<sup>9</sup> <= nums[i] <= 10<sup>9</sup></code></li>
</ul>


## template

```java
class Solution {
	public int longestConsecutive(int[] nums) {
		Set<Integer> num_set = new HashSet<Integer>();
		for (int num : nums) {
			num_set.add(num);
		}

		int longestStreak = 0;

		for (int num : num_set) {
			if (!num_set.contains(num - 1)) {
				int currentNum = num;
				int currentStreak = 1;

				while (num_set.contains(currentNum + 1)) {
					currentNum += 1;
					currentStreak += 1;
				}

				longestStreak = Math.max(longestStreak, currentStreak);
			}
		}

		return longestStreak;
	}
}


```

## 答案

```java

```

## 选项

### A

```java

```

### B

```java

```

### C

```java

```