Longest sequence count

longest-sequence-count.ts

/*
 * You are given an unsorted array/list 'ARR' of 'N'  integers.
 * Your task is to return the length of the longest consecutive sequence.
 * The consecutive sequence is in the form ['NUM', 'NUM' + 1, 'NUM' + 2, ..., 'NUM' + L]
 * where 'NUM' is the starting integer of the sequence and 'L' + 1 is the length of the sequence.
 */

function getHighestSequence(nums) {
    const numIndex = {};
    let highestPatternNumber = 0;
    function safeUpdateHashmap(key, value) {
        if (key in numIndex) {
            numIndex[key] = value;
        }
    }
    for (let num of nums) {
        num = parseInt(num);
        if (numIndex[num]) {
            continue;
        }
        const nextNum = num + 1;
        const prevNum = num - 1;
        const nextNumSeqCnt = numIndex[nextNum] || 0;
        const prevNumSeqCnt = numIndex[prevNum] || 0;
        const sequenceCount = 1 + nextNumSeqCnt + prevNumSeqCnt;
        const prevHighestSequence = numIndex[highestPatternNumber] || 0;
        const isHighestSequence = sequenceCount > prevHighestSequence;
        const tail = prevNumSeqCnt && num - prevNumSeqCnt;
        const head = nextNumSeqCnt && num + nextNumSeqCnt;
        if (isHighestSequence) {
            highestPatternNumber = tail || head || num;
        }
        safeUpdateHashmap(tail, sequenceCount);
        safeUpdateHashmap(head, sequenceCount);
        // console.log(JSON.stringify({ num, isHighestSequence, prevHighestSequence, sequenceCount, highestPatternNumber, nextNum, prevNum, nextNumSeqCnt, prevNumSeqCnt, tail, head }));
        numIndex[num] = sequenceCount;
    }
    // console.log(JSON.stringify({ nums, numIndex, highestPatternNumber }));
    return numIndex[highestPatternNumber];
}

const testCases = [
  { input: [0, 0], output: 1 },
  { input: [1, 2, 0, 1], output: 3 },
  { input: [100, 4, 200, 1, 3, 2], output: 4 },
  { input: [100000000], output: 1 },
  { input: [100, 100, 100, 100, 99, 101, 101, 101, 101, 101], output: 3 },
  { input: [2, 2, 2, 1, 9], output: 2 },
];

for (testCase of testCases) {
  const { input, output } = testCase;
  const actualOutput = getHighestSequence(testCase.input);
  console.log({ input, output, actualOutput });
}

;