Solution Explanation:

The problem asks to find the lexicographically smallest string of length n with a numeric value of k. The numeric value of a string is the sum of the numeric values of its characters (a=1, b=2, ..., z=26).

The solution employs a greedy approach. The core idea is to prioritize using smaller characters ('a') as much as possible while ensuring the numeric value constraint (k) is met.

Algorithm:

1. Initialization: Create a string ans of length n, filled with 'a' characters (the lexicographically smallest characters). The initial numeric value is n (all 'a's).

2. Remaining Value: Calculate the remaining numeric value needed: d = k - n. This is how much more numeric value we need to add to reach k.

3. Greedy Assignment: Iterate through the string from right to left (index i from n-1 to 0). In each iteration:

   • If d is greater than 25 (the maximum value of a single character), we can set the current character to 'z' (to minimize the lexicographical order) and reduce d by 25.
   • Otherwise, we add the remaining d to the current character's value ('a' + d) and terminate the loop. This ensures that we don't exceed k.

4. Return: Convert the character array ans to a string and return it.

Time and Space Complexity:

• Time Complexity: O(n). The algorithm iterates through the string once in the worst case.
• Space Complexity: O(n) to store the resulting string. If we ignore the space for the output string, the space complexity is O(1) as we only use a few integer variables.

Code Explanations (Python Example):

class Solution:
    def getSmallestString(self, n: int, k: int) -> str:
        ans = ['a'] * n  # Initialize with 'a's
        i, d = n - 1, k - n # i: index, d: remaining value
 
        while d > 25:  # While remaining value > 25, use 'z'
            ans[i] = 'z'
            d -= 25
            i -= 1
 
        ans[i] = chr(ord(ans[i]) + d) # Add the remaining value to the current character
 
        return ''.join(ans) # Join the characters into a string

The other languages (Java, C++, Go) follow the same logic, with minor syntactic differences to handle strings and character manipulation. The core greedy approach remains consistent across all implementations.