Repeated DNA Sequences - LeetCode javascript solutions

Problem

The DNA sequence is composed of a series of nucleotides abbreviated as 'A', 'C', 'G', and 'T'.

For example, "ACGAATTCCG" is a DNA sequence.

When studying DNA, it is useful to identify repeated sequences within the DNA.

Given a string s that represents a DNA sequence, return all the 10-letter-long sequences (substrings) that occur more than once in a DNA molecule. You may return the answer in any order.

Example 1:

Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT"
Output: ["AAAAACCCCC","CCCCCAAAAA"]

Example 2:

Input: s = "AAAAAAAAAAAAA"
Output: ["AAAAAAAAAA"]

Constraints:

1 <= s.length <= 105
s[i] is either 'A', 'C', 'G', or 'T'.

Solution

/**
 * @param {string} s
 * @return {string[]}
 */
var findRepeatedDnaSequences = function(s) {
    var res = [];
    var map = {};
    for (var i = 0; i <= s.length - 10; i++) {
        var str = s.slice(i, i + 10);
        var num = map[str];
        if (num === -1) continue;
        if (num === 1) {
            map[str] = -1;
            res.push(str);
            continue;
        }
        map[str] = 1;
    }
    return res;
};

Explain:

nope.

Complexity:

Time complexity : O(n).
Space complexity : O(1).