187. Repeated-DNA-Sequencesh

/**
 * @param {string} s
 * @return {string[]}
 */
var findRepeatedDnaSequences = function(s) {
    let hash_map = {}
    s = s.split("")
    let sequence = s.slice(0,9)
    let res = [];

    for(let i = 9; i < s.length; i++){
        sequence.push(s[i]);
        let key = sequence.join('');
        if(!(key in hash_map))
            hash_map[key] = 0;
        hash_map[key]++;
        if(hash_map[key] === 2)
            res.push(key)
        sequence.shift();

    }
    
    return res;
    
};



class Solution:
    def findRepeatedDnaSequences(self, s: str) -> List[str]:
        sequence_count = Counter()
        repeated_sequence = []
        num_substrings = len(s) - 10
        for i in range(num_substrings + 1):
            subsequence = s[i:i+10]
            sequence_count[subsequence] += 1
            if sequence_count[subsequence] == 2:
                repeated_sequence.append(subsequence)
        
        return repeated_sequence