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Longest Consecutive Sequence

Explore how to solve the longest consecutive sequence problem in an unsorted array using the union find algorithm. This lesson guides you through understanding the problem constraints and implementing a solution that connects elements efficiently. By mastering this pattern, you will enhance your ability to tackle similar graph-related coding interview challenges.

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Statement

Given an unsorted array, nums, your task is to return the length of the longest consecutive sequence of elements. The consecutive sequence of elements is such that there are no missing elements in the sequence. The consecutive elements can be present anywhere in the input array.

Note: Two elements, xx and yy, are called consecutive if the difference between them is equal to 11.

Constraints:

  • 0≤0 \leq nums.lengths ≤103\leq 10^{3}
  • −106≤-10^{6} \leq nums[i] ≤106\leq 10^{6}

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Longest Consecutive Sequence

1.

What is the output if the following numbers array is given as input?

nums = [1,3,2][1, 3, 2]

A.

11

B.

00

C.

33

D.

44

1 / 4

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4

Try it yourself

Implement your solution in LongestConsecutive.java in the following coding playground. The supporting code template provided in UnionFind.java is meant to assist in developing your solution to the problem.

Java
usercode > LongestConsecutive.java
/*
⬅️ We have provided a UnionFind.java file under the "Files" tab 
of this widget. You can use this file to build your solution.
*/
public class LongestConsecutive{
    
    public static int longestConsecutiveSequence(int[] nums) {
        
        // Replace this placeholder return statement with your code
        
        return 0;
    }
}
Longest Consecutive Sequence