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1663. Smallest String With A Given Numeric Value

The numeric value of a lowercase character is defined as its position (1-indexed) in the alphabet, so the numeric value of a is 1, the numeric value of b is 2, the numeric value of c is 3, and so on.

The numeric value of a string consisting of lowercase characters is defined as the sum of its characters' numeric values. For example, the numeric value of the string "abe" is equal to 1 + 2 + 5 = 8.

You are given two integers n and k. Return the lexicographically smallest string with length equal to n and numeric value equal to k.

Note that a string x is lexicographically smaller than string y if x comes before y in dictionary order, that is, either x is a prefix of y, or if i is the first position such that x[i] != y[i], then x[i] comes before y[i] in alphabetic order.

Example 1:

Input: n = 3, k = 27
Output: "aay"
Explanation: The numeric value of the string is 1 + 1 + 25 = 27, and it is the smallest string with such a value and length equal to 3.

Example 2:

Input: n = 5, k = 73
Output: "aaszz"

Constraints:

• 1 <= n <= 105
• n <= k <= 26 * n

Solutions (Ruby)

1. Greedy

# @param {Integer} n
# @param {Integer} k
# @return {String}
def get_smallest_string(n, k)
  k == 26 * n ? 'z' * n : 'a' * (n - (k - n) / 25 - 1) + (97 + (k - n) % 25).chr + 'z' * ((k - n) / 25)
end

Solutions (Rust)

1. Greedy

use std::iter;

impl Solution {
    pub fn get_smallest_string(n: i32, k: i32) -> String {
        if k == 26 * n {
            "z".repeat(n as usize)
        } else {
            iter::repeat('a')
                .take((n - (k - n) / 25 - 1) as usize)
                .chain(iter::once((97 + (k - n) % 25) as u8 as char))
                .chain(iter::repeat('z').take(((k - n) / 25) as usize))
                .collect()
        }
    }
}