## Question

Given an unsorted array, find the length of the longest sequence of consecutive numbers in the array.

eg.

`consecutive([4, 2, 1, 6, 5]) = 3, [4, 5, 6]`

`consecutive([5, 5, 3, 1]) = 1, [1], [3], or [5]`

Once you think that you’ve solved the problem, click below to see the solution.

*As always, remember that practicing coding interview questions is as much about how you practice as the question itself. Make sure that you give the question a solid go before skipping to the solution. Ideally if you have time, write out the solution first by hand and then only type it into your computer to verify your work once you've verified it manually. To learn more about how to practice, check out this blog post.*

## Solution

How was that problem? You can check out the solution in the video below.

Here is the source code for the solution shown in the video (Github):

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public static int consecutive(int[] a) { // Put all the values into a HashSet HashSet<Integer> values = new HashSet(); for (int i : a) { values.add(i); } // For each value, check if its the first in a sequence of consecutive // numbers and iterate through to find the length of the consecutive // sequence int maxLength = 0; for (int i : values) { // If it is not the leftmost value in the sequence, don't bother if (values.contains(i - 1)) continue; int length = 0; // Iterate through sequence while (values.contains(i++)) length++; maxLength = Math.max(maxLength, length); } return maxLength; } |

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