| ||||||||||
Online Judge | Problem Set | Authors | Online Contests | User | ||||||
---|---|---|---|---|---|---|---|---|---|---|
Web Board Home Page F.A.Qs Announcement | Current Contest Past Contests Scheduled Contests Award Contest |
Walking Race
Description flymouse¡¯s
sister wc is very capable at sports and her favorite event is walking
race. Chasing after the championship in an important competition, she
comes to a training center to attend a training course. The center has N check-points numbered 1 through N.
Some pairs of check-points are directly connected by two-way paths. The
check-points and the paths form exactly a tree-like structure. The
course lasts N days. On the i-th day, wc picks check-point i
as the starting point and chooses another check-point as the finishing
point and walks along the only simple path between the two points for
the day¡¯s training. Her choice of finishing point will make it that the
resulting path will be the longest among those of all possible choices. After
every day¡¯s training, flymouse will do a physical examination from
which data will obtained and analyzed to help wc¡¯s future training be
better instructed. In order to make the results reliable, flymouse is
not using data all from N days for analysis. flymouse¡¯s model
for analysis requires data from a series of consecutive days during
which the difference between the longest and the shortest distances wc
walks cannot exceed a bound M. The longer the series is, the
more accurate the results are. flymouse wants to know the number of
days in such a longest series. Can you do the job for him? Input The input contains a single test case. The test case starts with a line containing the integers N (N ¡Ü 106) and M (M < 109). Then follow N − 1 lines, each containing two integers fi and di (i = 1, 2, ¡, N − 1), meaning the check-points i + 1 and fi are connected by a path of length di. Output Output one line with only the desired number of days in the longest series. Sample Input Sample Output Hint Explanation for the sample: There
are three check-points. Two paths of lengths 1 and 3 connect
check-points 2 and 3 to check-point 1. The three paths along with wc
walks are 1-3, 2-1-3 and 3-1-2. And their lengths are 3, 4 and 4.
Therefore data from all three days can be used for analysis. Source |
[Submit] [Go Back] [Status] [Discuss]
All Rights Reserved 2003-2006 Ying Fuchen,Xu Pengcheng,Xie Di
Any problem, Please Contact Administrator