longestconssubseq.js

function longestConsecutiveSubsequence(arr) {
  arr.sort((a, b) => a - b); // Step 1
  let longestSubsequence = 1; // Step 2
  let currentSubsequence = 1; // Step 3

  for (let i = 1; i < arr.length; i++) { // Step 4
    if (arr[i] === arr[i - 1] + 1) { // Step 5
      currentSubsequence++;
      if (currentSubsequence > longestSubsequence) { // Step 6
        longestSubsequence = currentSubsequence;
      }
    } else { // Step 7
      currentSubsequence = 1;
    }
  }

  return longestSubsequence; // Step 8
}

const arr = [1, 2, 3, 5, 6, 7, 9, 10, 11];
console.log(longestConsecutiveSubsequence(arr)); // Output: 3 (because the longest consecutive subsequence is 9, 10, 11)