Leetcode 128 Longest Consecutive Sequence

 In here, I would like to discuss the dynamic set in Leetcode 128 Longest Consecutive Sequence.

This is my solution: 

• Put all numbers into set.
• The find the first number of each sequence. The first number is the number without any previous number (n-1) in the set.
• Loop through the next number (n+1). And find out the max count. (Remove the current number from set in order to iterate it again.)

var longestConsecutive = function(nums) {

    

    let set = new Set(nums);

    let maxLen = 0;

    function next(num) {

        if (set.has(num)) {

            //set.delete(num);

            return next(num + 1) + 1;

        } else {

            return 0;

        }

    }

    console.log(set);

    for (let num of nums) {

        //console.log(num);

        let pre = num - 1;

        if (!set.has(pre)) {

            let len = next(num+1) + 1;

            if (len > maxLen) {

                maxLen = len;

            }

        }

    }

    return maxLen;

};

 

The particular I would discuss is 

Remove the current number from set in order to iterate it again.

set.delete(num)

I would say that can be optimize performance. However, base on the leetcode submission result, dynamic changing set is actually a performance penalty.