不会做。打表打不起来，只知道规律。
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1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| 1 |
1 |
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|
|
|
|
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| 2 |
2 |
2 |
|
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|
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| 3 |
3 |
5 |
5 |
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| 4 |
4 |
9 |
14 |
14 |
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| 5 |
5 |
14 |
28 |
42 |
42 |
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| 6 |
6 |
20 |
48 |
90 |
132 |
132 |
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| 7 |
7 |
27 |
75 |
165 |
297 |
429 |
429 |
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规律：
a[i][1]=i;
a[i][i]=a[i][i-1];
a[i][j]=a[i-1][j]+a[i][j-1];
Problem Description
Recently, lxhgww received a task : to generate strings contain ‘0‘s and ‘1‘s only, in which ‘0‘ appears exactly m times, ‘1‘ appears exactly n times. Also, any prefix string of it must satisfy the situation that the number of 1‘s can not be smaller than the number of 0‘s . But he can‘t calculate the number of satisfied strings. Can you help him?
Input
T(T<=100) in the first line is the case number.
Each case contains two numbers n and m( 1 <= m <= n <= 1000000 ).
Output
Output the number of satisfied strings % 20100501.
Sample Input
Sample Output
hdu 3398 String
原文：http://www.cnblogs.com/zufezzt/p/4484852.html
