SmallestStringWithAGivenNumeric.java

/*

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"

*/

class Solution {
    public String getSmallestString(int n, int k) {
        char[] result = new char[n];
        for (int i = 0; i < n; i++) {
            result[i] = 'a';//initialize all array element with 'a'
            k--;
        }
        int numValue;
        while (k > 0) {
            numValue = Math.min(25, k);//building the string from the end to the beginning, it will always be optimal.
            result[--n] += numValue;
            k -= numValue;
        }
        return String.valueOf(result);   
    }
}