Kata

Given an array of large numbers represented as BigInteger[] arr and a set of queries (int[,] queries), your task is to determine the frequency of a specific digit within a given range of the array.

Each query has the form [L, R, X], where:

• L is the start index (inclusive) of the subarray.
• R is the end index (inclusive) of the subarray.
• X is the target digit whose frequency you need to count.

Input:

• An array of BigInteger[] arr, where each element is a large number.
• A matrix queries, where each row is a query in the format [L, R, X].

Output:

Return an array of integers where each element corresponds to the frequency of the digit X in the subarray arr[L..R].

Examples:

BigInteger[] arr = { new BigInteger(222), new BigInteger(54888), new BigInteger(321), 
                     new BigInteger(1000), new BigInteger(5840000003), new BigInteger(334491) };
int[,] queries = { {0, 1, 2}, {1, 4, 8}, {4, 5, 7} };

FrequencyDigits(arr, queries) 
// Output: {3, 4, 0}

Explanation:

• Query [0, 1, 2]:

  • Subarray: { 222, 54888 }
  • Target digit: 2
  • Result: The digit 2 appears 3 times in the subarray.

• Query [1, 4, 8]:

  • Subarray: { 54888, 321, 1000, 5840000003 }
  • Target digit: 8
  • Result: The digit 8 appears 4 times in the subarray.

• Query [4, 5, 7]:

  • Subarray: { 5840000003, 334491 }
  • Target digit: 7
  • Result: The digit 7 does not appear in the subarray.

Note:

• It is important that the solution is efficient, especially for large arrays and a large number of queries.