1663. Smallest String With A Given Numeric Value

Description

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

Solution: Greedy

• Time complexity: O(n)
• Space complexity: O(n)

 

JavaScript

/**
 * @param {number} n
 * @param {number} k
 * @return {string}
 */
const getSmallestString = function (n, k) {
  const CODE_BASE = 'a'.charCodeAt(0);
  const result = new Array(n).fill('a');

  k -= n;

  for (let index = n - 1; index >= 0; index--) {
    const code = Math.min(25, k);
    const targetChar = String.fromCharCode(CODE_BASE + code);

    result[index] = targetChar;
    k -= code;
    if (k === 0) break;
  }
  return result.join('');
};