LeetCode in Kotlin
2180. Count Integers With Even Digit Sum
Easy
Given a positive integer num, return the number of positive integers less than or equal to num whose digit sums are even.
The digit sum of a positive integer is the sum of all its digits.
Example 1:
Input: num = 4
Output: 2
Explanation:
The only integers less than or equal to 4 whose digit sums are even are 2 and 4.
Example 2:
Input: num = 30
Output: 14
Explanation:
The 14 integers less than or equal to 30 whose digit sums are even are
2, 4, 6, 8, 11, 13, 15, 17, 19, 20, 22, 24, 26, and 28.
Constraints:
1 <= num <= 1000
Solution
class Solution {
fun countEven(num: Int): Int {
// Digit sum of the last number, we can get each digit this way sicne the range is [1, 1000]
val sum = num % 10 + num / 10 % 10 + num / 100 % 10 + num / 1000 % 10
// Check the parity of the digit sum of the last number
return (num - (sum and 1)) / 2
}
}