TopCoder Problem Statement - Iditarod |

Single Round Match 160 Round 1 - Division I, Level One |

Determine the average number of minutes contestants needed to complete a multi-day race.

01: public class Iditarod { 02: 03: public int avgMinutes(String[] times) { 04: 05: int totalMinutes = 0; 06: 07: // Add up the total minutes for each finishing time. 08: for (String t : times) { 09: totalMinutes += calcMinutes(t); 10: } 11: 12: // Get the average. 13: double avg = (double) totalMinutes / (double) times.length; 14: 15: // Round off by adding .5 and truncating. 16: avg += 0.5; 17: return (int) avg; 18: } 19: 20: private static int calcMinutes(String s) { 21: 22: // Format is: hh:mm xM, DAY n 23: 24: int hours = Integer.parseInt(s.substring(0,2)); 25: int minutes = Integer.parseInt(s.substring(3,5)); 26: boolean isPM = (s.charAt(6) == 'P'); 27: 28: // Handles both 1 and 2 digit day lengths. 29: int day = Integer.parseInt(s.substring(14, s.length())); 30: 31: // Handle 12 PM and 12 AM hours 32: if (hours == 12) { 33: if (isPM) { 34: hours = 0; 35: } else { 36: hours = 24; 37: day -= 1; 38: } 39: } 40: 41: if (isPM) hours += 12; 42: 43: // Subtract off the start time. 44: hours -= 8; 45: 46: // Minutes per day, times number of days (don't count day 1) 47: int totalMinutes = (24*60) * (day - 1); 48: 49: totalMinutes += (60 * hours); 50: 51: totalMinutes += minutes; 52: 53: return totalMinutes; 54: } 55: 56: }

Not much difficulty here. avgMinutes() loops through all the finishing times and keeps a running total of the number of minutes for all the competitors to finish. Then it just divides the today by the number of times - casting to double to avoid losing decimal places. To round off, just add 0.5 and truncate - a trick everyone should know. There's no danger of overflow here, so just stick with the simplest thing that works.

Calculating the number of minutes for a given time is also pretty simple. We just need to take care dealing with the 12:00 PM and 12:00 AM hours. Here, if it's 12 PM, I set the hours to 0. If it's 12 AM, I set hours to 24, and subtract a day. Then for any PM times, I add 12 hours. It may take a minute to think it through, but it's not tough. Remember to subtract off the 8:00 AM starting time. Then it's just a matter of adding up the number of minutes in a day, an hour, and the minutes portion.

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