2013WorksApplication笔试题之我见Problem1

题目1：

意思为一天从00：00到24.00（24.00为第二天的0.00)。我们不能在同一时间工作任务超过2件，意思就是我们在一时间只能做一项工作。 而每一项工作是一个时间段。比如工作1是

[08:00]到[12:00],工作2是[06:00]到[09:00].现在给你一个天的工作安排。求最大的同时工作数。比如工作1和工作2就是在8点到9点之间是同时工作。注：[08:00，09：00]与[09.00,10:00]两个工作也是overlapped because include "09:00"

下面是我的解法

public class Problem1 {


	public int getMaxIntervalOverlapCount(List<Interval> intervals) {
		int max_size = 1440;
		if (intervals == null||intervals.size()==0)
			return 0;
		int[] a = new int[max_size];
		int[] b = new int[intervals.size() * 2];
		int begin;
		int end;
		int num = 0;
		int maxOverlapCount = 0;
		Iterator<Interval> iterator = intervals.iterator();
		while (iterator.hasNext()) {
			Interval t = iterator.next();
			begin = t.getBeginMinuteUnit();
			end = t.getEndMinuteUnit();
			addArray(begin, end, a);
			b[num] = t.getBeginMinuteUnit();
			b[num + 1] = t.getEndMinuteUnit();
			num = num + 2;
		}
		
		// the maxOverlapCount can be found these points.
		maxOverlapCount = a[b[0]];
		for (int i = 1; i < b.length; i++) {
			if (maxOverlapCount < a[b[i]]) {
				maxOverlapCount = a[b[i]];
			}
		}
		return maxOverlapCount;
	}
    /**
     * Set the array from the begin to the end to plus one with itself.It means how much works
     * will be take in this time.
     * <pre>
     * when a[i] = 0. it means no works at this time.
     * and when a[i] = x. it means x works will take in this time.
     * @author jason
     * @param begin
     * @param end
     * @param a
     */
	private void addArray(int begin, int end, int[] a) {
		for (int i = begin; i <= end; i++)
			a[i]++;
	}

}

我的想法：时间Unit其实就是0-1440的一个分部。每一个工作对应该数轴上一条线段。每一个点上存在一条线段就记录加1，这样即是求该数轴上最大值的点。并且该点必然为某个工作的线段端点。

时间片段类定义：

public class Interval {
	private static class Time {
		final int hour;
		final int minute;

		public Time(int hour, int minute) {
			this.hour = hour;
			this.minute = minute;
		}

		@Override
		public boolean equals(Object obj) {
			if (!(obj instanceof Time)) {
				return false;
			}
			Time other = (Time) obj;
			return (this.hour == other.hour && this.minute == other.minute);
		}

		@Override
		public int hashCode() {
			return toString().hashCode();
		}

		@Override
		public String toString() {
			return String.format("%02d:%02d", hour, minute);
		}

	};

	private final Time begin;
	private final Time end;

	public Interval(String begin, String end) {
		this.begin = toTime(begin);
		this.end = toTime(end);
	}

	private static Time toTime(String timeFormatString) {
		Pattern p = Pattern.compile("(\\d?\\d):([0-5]\\d)");
		Matcher m = p.matcher(timeFormatString);
		if (!m.find()) {
			throw new IllegalArgumentException("invalid time format");
		}
		int hour = Integer.parseInt(m.group(1));
		int minute = Integer.parseInt(m.group(2));
		return new Time(hour, minute);
	}

	public String getBegin() {
		return this.begin.toString();
	}

	public String getEnd() {
		return this.end.toString();
	}

	public int getBeginHour() {
		return this.begin.hour;
	}

	public int getBeginMinute() {
		return this.begin.minute;
	}

	public int getEndHour() {
		return this.end.hour;
	}

	public int getEndMinute() {
		return this.end.minute;
	}

	public int getBeginMinuteUnit() {
		return getBeginHour() * 60 + getBeginMinute();
	}
	public int getEndMinuteUnit(){
		return getEndHour()*60+getEndMinute();
	}
	public int getIntervalMinute() {
		return getEndMinuteUnit()-getBeginMinuteUnit();
	}

	@Override
	public boolean equals(Object obj) {

		if(!(obj instanceof Interval)) {
			return false;
		}
		Interval other =(Interval) obj;
		return (this.begin.equals(other.begin))&&(this.end.equals(other.end));
	}

	@Override
	public int hashCode() {

		return toString().hashCode();
	}

	@Override
	public String toString() {

		return String.format("[%s-%s]", begin,end);
	}
	
}