1663. Smallest String With A Given Numeric Value

Problem Link

Description

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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

Solution

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Python3

class Solution:
    def getSmallestString(self, n: int, k: int) -> str:
        last = []
        
        while k >= 26 + n:
            last.append("z")
            n -= 1
            k -= 26
            
        first = []
        for i in range(n):
            if i == n - 1:
                first.append(chr(ord("a") + k - 1))
            else:
                first.append("a")
                k -= 1
        
        return "".join(first + last)