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2576. Minimum Penalty For A Shop

String Prefix Sum

Problem - Minimum Penalty For A Shop

Medium

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

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class Solution:
    def bestClosingTime(self, customers: str) -> int:
        result = 0
        min_pen = cost = customers.count("Y")
        for j, char in enumerate(customers, 1):
            cost += 1 if char == "N" else -1
            if cost < min_pen:
                result = j
                min_pen = cost

        return result

Submission Stats:

  • Runtime: 51 ms (74.58%)
  • Memory: 17.9 MB (92.15%)