LeetCode-in-Java

3723. Maximize Sum of Squares of Digits

Medium

You are given two positive integers num and sum.

A positive integer n is good if it satisfies both of the following:

• The number of digits in n is exactly num.
• The sum of digits in n is exactly sum.

The score of a good integer n is the sum of the squares of digits in n.

Return a string denoting the good integer n that achieves the maximum score. If there are multiple possible integers, return the maximum one. If no such integer exists, return an empty string.

Example 1:

Input: num = 2, sum = 3

Output: “30”

Explanation:

There are 3 good integers: 12, 21, and 30.

• The score of 12 is 12 + 22 = 5.
• The score of 21 is 22 + 12 = 5.
• The score of 30 is 32 + 02 = 9.

The maximum score is 9, which is achieved by the good integer 30. Therefore, the answer is "30".

Example 2:

Input: num = 2, sum = 17

Output: “98”

Explanation:

There are 2 good integers: 89 and 98.

• The score of 89 is 82 + 92 = 145.
• The score of 98 is 92 + 82 = 145.

The maximum score is 145. The maximum good integer that achieves this score is 98. Therefore, the answer is "98".

Example 3:

Input: num = 1, sum = 10

Output: “”

Explanation:

There are no integers that have exactly 1 digit and whose digits sum to 10. Therefore, the answer is "".

Constraints:

• 1 <= num <= 2 * 105
• 1 <= sum <= 2 * 106

Solution

public class Solution {
    public String maxSumOfSquares(int places, int sum) {
        String ans = "";
        int nines = sum / 9;
        if (places < nines) {
            return ans;
        } else if (places == nines) {
            int remSum = sum - nines * 9;
            if (remSum > 0) {
                return ans;
            }
            ans = "9".repeat(nines);
        } else {
            int remSum = sum - nines * 9;
            ans = "9".repeat(nines) + remSum;
            int extra = places - ans.length();
            if (extra > 0) {
                ans = ans + ("0".repeat(extra));
            }
        }
        return ans;
    }
}

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