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  • hdu 3398 String

    2018.04.05 update: 今天无意间重新翻开了博客发现了这个历史遗留问题,已经知道是卡特兰数了,但由于取模的数不是素数啊。。。好像还是不太会做。

    -----------------

    不会做。打表打不起来,只知道规律。

      1 2 3 4 5 6 7 8
    1 1              
    2 2 2            
    3 3 5 5          
    4 4 9 14 14        
    5 5 14 28 42 42      
    6 6 20 48 90 132 132    
    7 7 27 75 165 297 429 429  
     

    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
    1 2 2
    Sample Output
    2
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  • 原文地址:https://www.cnblogs.com/zufezzt/p/4484852.html
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