AtCoder Grand Contest 012
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Problem Statement
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Snuke arranged $N$ colorful balls in a row. The $i$-th ball from the left has color $c_i$ and weight $w_i$.
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He can rearrange the balls by performing the following two operations any number of times, in any order:
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- Operation
$1$: Select two balls with the same color. If the total weight of these balls is at most$X$, swap the positions of these balls. - Operation
$2$: Select two balls with different colors. If the total weight of these balls is at most$Y$, swap the positions of these balls.
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How many different sequences of colors of balls can be obtained? Find the count modulo $10^9 + 7$.
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Constraints
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$1 ≤ N ≤ 2 × 10^5$$1 ≤ X, Y ≤ 10^9$$1 ≤ c_i ≤ N$$1 ≤ w_i ≤ 10^9$$X, Y, c_i, w_i$are all integers.
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Input
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Input is given from Standard Input in the following format:
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N X Y
c_1 w_1
:
c_N w_N
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Output
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Print the answer.
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样例
Input #1
4 7 3
3 2
4 3
2 1
4 4
Output #1
2
- The sequence of colors $(2,4,3,4)$ can be obtained by swapping the positions of the first and third balls by operation $2$.
- It is also possible to swap the positions of the second and fourth balls by operation $1$, but it does not affect the sequence of colors.
Input #2
1 1 1
1 1
Output #2
1
Input #3
21 77 68
16 73
16 99
19 66
2 87
2 16
7 17
10 36
10 68
2 38
10 74
13 55
21 21
3 7
12 41
13 88
18 6
2 12
13 87
1 9
2 27
13 15
Output #3
129729600
题目信息
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。