Alarm Clock 的问题求解

Question

Problem Description
Advanced courses in computer science often include many interesting optimization problems. The following optimization problem is not advanced, nor is it particularly interesting. You are to write a program to determine the minimum number of buttons a person must push to set their alarm clock. Assume the alarm clock has 7 buttons – hour-up, hour-down, tens-minute-up, and tens-minute-down, ones-minute-up, ones-minute-down, and am/pm. For example, continuously pushing the hour-up button will cause hour digit to go through the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, …. Pushing the hour-down button will cause the sequence to go in the reverse order. Pushing the tens-minute-up buttons cycles tens minute digit through the numbers 0, 1, 2, 3, 4, 5, 0, 1, … Pushing the ones-minute-up button cycles the one digit through the numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, … Pushing the am/pm button causes toggles the am/pm indicator.

Input
The first line of input will contain an integer indicating the number of problems that need to be processed. Each line will contain two times – the first one the current time and the second one the desired time. All times will have the format: 1 or 2-digit hour; followed by a colon; followed by a 2-digit minute; followed by “am” or “pm”. A single space will separate the two times.

Output
Your program should produce one line of output for each problem using one of two formats: ”Going from 7:30am to 7:33am requires 3 pushes.” or “Going from 7:30am to 7:20am requires 1 push.”

Sample Input
6
7:30am 7:30am
7:30am 7:33am
7:30am 7:20am
7:30am 7:27am
7:30am 7:30pm
7:10am 7:50am

Sample Output
Going from 7:30am to 7:30am requires 0 pushes.
Going from 7:30am to 7:33am requires 3 pushes.
Going from 7:30am to 7:20am requires 1 push.
Going from 7:30am to 7:27am requires 4 pushes.
Going from 7:30am to 7:30pm requires 1 push.
Going from 7:10am to 7:50am requires 2 pushes.

Answer 1

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# read data
data <- readLines()

# split into list of times
times <- unlist(strsplit(data, "\n"))

# define function to count pushes needed
pushes_needed <- function(hour, minutes) {
  # convert to integers
  hours <- as.integer(hour)
  minutes <- as.integer(minutes)

  # calculate number of pushes needed
  if (hours == 24 && minutes > 30) {
    return(0)
  } else if (minutes < 30) {
    return(1)
  } else if (minutes == 30) {
    return(3)
  } else if (minutes >= 30 && minutes <= 39) {
    return(4)
  } else if (minutes == 40 || minutes == 41) {
    return(5)
  } else if (minutes == 42 || minutes == 43 || minutes == 44) {
    return(6)
  }
}

# apply function to each time
results <- sapply(times, pushes_needed)

# print results
print(results)