一道ACM题求大神指导是怎么推出周期的?
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一道ACM题求大神指导是怎么推出周期的?
Problem Description A number sequence is defined as follows:f(1) = 1,f(2) = 1,f(n) = (A * f(n - 1) + B * f(n - 2)) mod 7.Given A,B,and n,you are to calculate the value of f(n).Input The input consists of multiple test cases.Each test case contains 3 integers A,B and n on a single line (1
Problem Description A number sequence is defined as follows:f(1) = 1,f(2) = 1,f(n) = (A * f(n - 1) + B * f(n - 2)) mod 7.Given A,B,and n,you are to calculate the value of f(n).Input The input consists of multiple test cases.Each test case contains 3 integers A,B and n on a single line (1
![一道ACM题求大神指导是怎么推出周期的?](/uploads/image/z/14978706-42-6.jpg?t=%E4%B8%80%E9%81%93ACM%E9%A2%98%E6%B1%82%E5%A4%A7%E7%A5%9E%E6%8C%87%E5%AF%BC%E6%98%AF%E6%80%8E%E4%B9%88%E6%8E%A8%E5%87%BA%E5%91%A8%E6%9C%9F%E7%9A%84%3F)
因为f(n)只有七中取值0-6,系数a对应7个,b对应7个,A * f(n - 1) + B * f(n - 2)) 只有49个不同值,为一个周期,只要开一个数组储存这49个值mod 7的余数就好了,然后用n%49,来算