README.md

2483. Minimum Penalty for a Shop

You are given the customer visit log of a shop represented by a 0-indexed string customers consisting only of characters 'N' and 'Y':

• if the ith character is 'Y', it means that customers come at the ith hour
• whereas 'N' indicates that no customers come at the ith hour.

If the shop closes at the jth hour (0 <= j <= n), the penalty is calculated as follows:

• For every hour when the shop is open and no customers come, the penalty increases by 1.
• For every hour when the shop is closed and customers come, the penalty increases by 1.

Return the earliest hour at which the shop must be closed to incur a minimum penalty.

Note that if a shop closes at the jth hour, it means the shop is closed at the hour j.

Example 1:

Input: customers = "YYNY"
Output: 2
Explanation:
- Closing the shop at the 0th hour incurs in 1+1+0+1 = 3 penalty.
- Closing the shop at the 1st hour incurs in 0+1+0+1 = 2 penalty.
- Closing the shop at the 2nd hour incurs in 0+0+0+1 = 1 penalty.
- Closing the shop at the 3rd hour incurs in 0+0+1+1 = 2 penalty.
- Closing the shop at the 4th hour incurs in 0+0+1+0 = 1 penalty.
Closing the shop at 2nd or 4th hour gives a minimum penalty. Since 2 is earlier, the optimal closing time is 2.

Example 2:

Input: customers = "NNNNN"
Output: 0
Explanation: It is best to close the shop at the 0th hour as no customers arrive.

Example 3:

Input: customers = "YYYY"
Output: 4
Explanation: It is best to close the shop at the 4th hour as customers arrive at each hour.

Constraints:

• 1 <= customers.length <= 105
• customers consists only of characters 'Y' and 'N'.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn best_closing_time(customers: String) -> i32 {
        let mut count_n = 0;
        let mut count_y = customers.chars().filter(|&c| c == 'Y').count();
        let mut min_penalty = count_n + count_y;
        let mut ret = 0;

        for (i, c) in customers.chars().enumerate() {
            if c == 'N' {
                count_n += 1;
            } else if c == 'Y' {
                count_y -= 1;
            }

            if min_penalty > count_n + count_y {
                min_penalty = count_n + count_y;
                ret = i + 1;
            }
        }

        ret as i32
    }
}