3945 - Digit Frequency Score

Description (leetcode)

You are given an integer n.

The score of n is defined as the sum of d * freq(d) over all distinct digits d, where freq(d) denotes the number of times the digit d appears in n.

Return an integer denoting the score of n.

Example 1:

Input: n = 122

Output: 5

Explanation:

• The digit 1 appears 1 time, contributing 1 * 1 = 1.
• The digit 2 appears 2 times, contributing 2 * 2 = 4.
• Thus, the score of n is 1 + 4 = 5.

Example 2:

Input: n = 101

Output: 2

Explanation:

• The digit 0 appears 1 time, contributing 0 * 1 = 0.
• The digit 1 appears 2 times, contributing 1 * 2 = 2.
• Thus, the score of n is 2.

Constraints:

• 1 <= n <= 10⁹

submission

impl Solution {
    pub fn digit_frequency_score(n: i32) -> i32 {
        std::iter::successors(Some(n), |n| Some(n / 10))
            .take_while(|n| n.is_positive())
            .fold(0, |acc, n| acc + n % 10)
    }
}