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.

Greedy Solution

• we start from end and try to add largest possible character in the string.
• return the string by reversing the order.
• TC: O(N)
• SC: O(1)

Code

class Solution {
public:
    string getSmallestString(int n, int k)
    {
        string ans = "";
        for (int i = 0; i < n; i++) {
            ans += 'a';
        }
        k -= n;
        int i = 0;
        while (k != 0) {
            if (k >= 25) {
                ans[i++] = 'z';
                k -= 25;
            } else {
                ans[i] = ans[i] + k;
                i++;
                reverse(ans.begin(), ans.end());
                return ans;
            }
        }
        reverse(ans.begin(), ans.end());
        return ans;
    }
};