# Longest Consecutive Sequence LeetCode Solution

Here, We see Longest Consecutive Sequence LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

# List of all LeetCode Solution

## Problem Statement

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

## Longest Consecutive Sequence LeetCode SolutionC++

``````class Solution {
public:
int longestConsecutive(vector<int>& nums) {
int n = nums.size();
if(n == 0){
return 0;
}
sort(nums.begin(), nums.end());
int currentConsecutiveSequence = 1;
int longestConsecutiveSequence = 0;
for(int i=1; i<n; i++){
if(nums[i] != nums[i-1]){
if(nums[i] == nums[i-1] + 1){
currentConsecutiveSequence++;
}
else{
longestConsecutiveSequence = max(longestConsecutiveSequence, currentConsecutiveSequence);
currentConsecutiveSequence = 1;
}
}
}
return max(longestConsecutiveSequence, currentConsecutiveSequence);
}
};```Code language: PHP (php)```

## Longest Consecutive Sequence LeetCode SolutionJava

``````class Solution {
public int longestConsecutive(int[] nums) {int result = 0;
if (nums.length > 0) {
if (nums.length < 1000) {
Arrays.sort(nums);
int current = 0;
for (int i = 1; i < nums.length; i++) {
if (nums[i] != nums[i - 1]) {
if (nums[i] - nums[i - 1] == 1) {
current++;
} else {
if (current + 1 > result) {
result = current + 1;
}
current = 0;
}
}
}
if (current + 1 > result) {
result = current + 1;
}
} else {
int min = Integer.MAX_VALUE;
int max = Integer.MIN_VALUE;
for (int num : nums) {
if (num > max) {
max = num;
}
if (num < min) {
min = num;
}
}
byte[] bits = new byte[max - min + 1];
for (int num : nums) {
bits[num - min] = 1;
}
int current = 0;
for (byte bit : bits) {
if (bit > 0) {
current++;
} else {
if (current > result) {
result = current;
}
current = 0;
}
}
if (current > result) {
result = current;
}
}
}
return result;
}
}```Code language: PHP (php)```

## Longest Consecutive Sequence SolutionJavaScript

``````var longestConsecutive = function(nums) {
if(nums.length==0) return 0
let count=1, max = 1
nums.sort((a, b) => a - b)
for(let i=0; i<nums.length; i++) {
if(nums[i]- nums[i-1] == 1) {
count=count+1 ;
max = Math.max(max, count)
}
else if(nums[i]==nums[i-1]) continue
else {
count = 1
}
}
return max
};```Code language: JavaScript (javascript)```

## Longest Consecutive Sequence SolutionPython

``````class Solution(object):
def longestConsecutive(self, nums):
longest = 0
num_set = set(nums)
for n in num_set:
if (n-1) not in num_set:
length = 1
while (n+length) in num_set:
length += 1
longest = max(longest, length)
return longest``````
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