LeetCode-in-Java

2195. Append K Integers With Minimal Sum

Medium

You are given an integer array nums and an integer k. Append k unique positive integers that do not appear in nums to nums such that the resulting total sum is minimum.

Return the sum of the k integers appended to nums.

Example 1:

Input: nums = [1,4,25,10,25], k = 2

Output: 5

Explanation: The two unique positive integers that do not appear in nums which we append are 2 and 3.

The resulting sum of nums is 1 + 4 + 25 + 10 + 25 + 2 + 3 = 70, which is the minimum.

The sum of the two integers appended is 2 + 3 = 5, so we return 5.

Example 2:

Input: nums = [5,6], k = 6

Output: 25

Explanation: The six unique positive integers that do not appear in nums which we append are 1, 2, 3, 4, 7, and 8.

The resulting sum of nums is 5 + 6 + 1 + 2 + 3 + 4 + 7 + 8 = 36, which is the minimum.

The sum of the six integers appended is 1 + 2 + 3 + 4 + 7 + 8 = 25, so we return 25.

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i] <= 109
• 1 <= k <= 108

Solution

import java.util.Arrays;

public class Solution {
    public long minimalKSum(int[] nums, int k) {
        Arrays.sort(nums);
        long sum = 0;
        int n = 0;
        for (int i = 0; i < nums.length; i++) {
            if (i == 0 || nums[i] != nums[i - 1]) {
                if (nums[i] - n > k) {
                    break;
                }
                sum += nums[i];
                n++;
            }
        }
        long t = n + (long) k;
        return (1 + t) * t / 2 - sum;
    }
}

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