Longest substring where all the characters appear at least K times | Set 3

<script>

    // Javascript program to implement 
    // the above approach
    
    // Function to find the length of
    // the longest substring
    function longestSubstring(s, k)
    {

        // Store the required answer
        let ans = 0;

        // Create a frequency map of the
        // characters of the string
        let freq = new Array(26);
        freq.fill(0);

        // Store the length of the string
        let n = s.length;

        // Traverse the string, s
        for (let i = 0; i < n; i++)

            // Increment the frequency of
            // the current character by 1
            freq[s[i].charCodeAt() - 
               'a'.charCodeAt()]++;

        // Stores count of unique characters
        let unique = 0;

        // Find the number of unique
        // characters in string
        for (let i = 0; i < 26; i++)
            if (freq[i] != 0)
                unique++;

        // Iterate in range [1, unique]
        for (let curr_unique = 1;
             curr_unique <= unique;
             curr_unique++)
        {

            // Initialize frequency of all
            // characters as 0
            for (let i = 0; i < freq.length; i++)
            {
                freq[i] = 0;
            }

            // Stores the start and the
            // end of the window
            let start = 0, end = 0;

            // Stores the current number of
            // unique characters and characters
            // occurring atleast K times
            let cnt = 0, count_k = 0;
            while (end < n)
            {
                if (cnt <= curr_unique)
                {
                    let ind = s[end].charCodeAt() - 
                              'a'.charCodeAt();

                    // New unique character
                    if (freq[ind] == 0)
                        cnt++;
                    freq[ind]++;

                    // New character which
                    // occurs atleast k times
                    if (freq[ind] == k)
                        count_k++;

                    // Expand window by
                    // incrementing end by 1
                    end++;
                }
                else
                {
                    let ind = s[start].charCodeAt() - 
                    'a'.charCodeAt();

                    // Check if this character
                    // is present atleast k times
                    if (freq[ind] == k)
                        count_k--;
                    freq[ind]--;

                    // Check if this character
                    // is unique
                    if (freq[ind] == 0)
                        cnt--;

                    // Shrink the window by
                    // incrementing start by 1
                    start++;
                }

                // If there are curr_unique
                // characters and each character
                // is atleast k times
                if (cnt == curr_unique
                    && count_k == curr_unique)

                    // Update the overall
                    // maximum length
                    ans = Math.max(ans, end - start);
            }
        }

        // Print the answer
        document.write(ans);
    }
    
    let S = "aabbba";
    let K = 3;
    longestSubstring(S, K);

</script>