# Longest Consecutive Sequence Leetcode Solution

In this post, we are going to solve the Longest Consecutive Sequence Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

## Problem

Given an unsorted array of integers `nums`, return the length of the longest consecutive elements sequence.

You must write an algorithm that runs in `O(n)` time.

Example 1:

```Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is `[1, 2, 3, 4]`. Therefore its length is 4.
```

Example 2:

```Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9
```

Constraints:

• `0 <= nums.length <= 105`
• `-109 <= nums[i] <= 109`

Now, lets see the leetcode solution of Longest Consecutive Sequence Leetcode Solution.

### Longest Consecutive Sequence Leetcode Solution in Python

```class Solution:
def longestConsecutive(self, nums: List[int]) -> int:
ans = 0
seen = set(nums)

for num in nums:
if num - 1 in seen:
continue
length = 0
while num in seen:
num += 1
length += 1
ans = max(ans, length)

return ans```

### Longest Consecutive Sequence Leetcode Solutionin CPP

```class Solution {
public:
int longestConsecutive(vector<int>& nums) {
int ans = 0;
unordered_set<int> seen{begin(nums), end(nums)};

for (int num : nums) {
// Num is the start of a sequence
if (seen.count(num - 1))
continue;
int length = 1;
while (seen.count(++num))
++length;
ans = max(ans, length);
}

return ans;
}
};```

### Longest Consecutive Sequence Leetcode Solution in Java

```class Solution {
public int longestConsecutive(int[] nums) {
int ans = 0;
Set<Integer> seen = Arrays.stream(nums).boxed().collect(Collectors.toSet());

for (int num : nums) {
// Num is the start of a sequence
if (seen.contains(num - 1))
continue;
int length = 1;
while (seen.contains(++num))
++length;
ans = Math.max(ans, length);
}

return ans;
}
}```

Note: This problem Longest Consecutive Sequence is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purpose.

Sharing Is Caring