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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: +---+---+---+---+--:+---+---+---+- ...
1111 1111
22222222 22222222
333333333333
|..................|
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.
Input:
- 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
Output:
- Line 1: A single integer that is the minimum number of segments required to cover all segments of the circumference of the corral.
Sample
Input 5 3 0 1 1 2 3 3 Output 2
Được gửi lên bởi: | sieunhan |
Ngày: | 2011-03-21 |
Thời gian chạy: | 1s |
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 |
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2011-03-23 18:18:22 Nguyễn Ðức Anh
Tôi bị điên nè hehehe Last edit: 2012-04-04 08:54:38 |