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CORRAL - Covering the Corral

The cows are so modest they want Farmer John to install covers
around the circular corral where they occasionally gather. The
corral has circumference C (1 <= C <= 1,000,000,000), and FJ can
choose from a set of M (1 <= M <= 100,000) covers that have fixed
starting points and sizes. At least one set of covers can surround
the entire corral.

Cover i can be installed at integer location x_i (distance from
starting point around corral) (0 <= x_i < C) and has integer length
l_i (1 <= l_i <= C).

FJ wants to minimize the number of segments he must install. What
is the minimum number of segments required to cover the entire
circumference of the corral?

Consider a corral of circumference 5, shown below as a pair of
connected line segments where both '0's are the same point on the
corral (as are both 1's, 2's, and 3's).

Three potential covering segments are available for installation:

Start Length
i x_i l_i
1 0 1
2 1 2
3 3 3

0 1 2 3 4 0 1 2 3 ...
corral: +---+---+---+---+--:+---+---+---+- ...
11111 1111
22222222 22222222

As shown, installing segments 2 and 3 cover an extent of (at least)
five units around the circumference. FJ has no trouble with the
overlap, so don't worry about that.



* Line 1: Two space-separated integers: C and M

* Lines 2..M+1: Line i+1 contains two space-separated integers: x_i
and l_i


5 3
0 1
1 2
3 3


* Line 1: A single integer that is the minimum number of segments
required to cover all segments of the circumference of the



Được gửi lên bởi:sieunhan
Thời gian chạy:0.770s
Giới hạn mã nguồn:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Ngôn ngữ cho phép:Tất cả ngoại trừ: ASM64 GOSU PERL6 PYPY RUST SED
Nguồn bài:Usaco Feb10 Gold

hide comments
2011-03-23 18:18:22 Nguyễn Ðức Anh
Tôi bị điên nè hehehe

Last edit: 2012-04-04 08:54:38
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