The i’th Fibonacci number f(i) is recursively defined in the following way: • f(0) = 0 and f(1) = 1 • f(i + 2) = f(i + 1) + f(i) for every i ≥ 0 Your task is to compute some values of this sequence.
Input
Input begins with an integer t ≤ 10, 000, the number of test cases. Each test case consists of three integers a, b, n where 0 ≤ a, b < 2 64 (a and b will not both be zero) and 1 ≤ n ≤ 1000.
Output
For each test case, output a single line containing the remainder of f(a b ) upon division by n.
Sample Input
3
1 1 2
2 3 1000
18446744073709551615 18446744073709551615 1000
Sample Output
1 21 250
题意:巨大的斐波那契,所有的计算都是对n取模,不妨设f(i) = (f(i-1) + f(i-2))%n;则根据分析最多进行n*n次循环就会出现重复序列,然后用快速幂求a的b次方的后n位数就是其在循环中的位置,具体分析可见紫书。
#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> using namespace std; typedef unsigned long long ll; int f[1000010]; int mod( ll a,ll b,int y){ int t = 1; while(b){ if(b%2 != 0){ t = (a*t)%y; b--; } a = (a*a)%y; b /= 2; } return t; } //int f[1000010]; int main() { ll a,b; int n,i,t,record; scanf("%d",&t); while(t--){ f[1] = f[2] = 1; cin>>a>>b>>n; if(a == 0 || n == 1){ printf("0 "); continue; } for(i = 3; i <= n*n+10; i++){ f[i] = (f[i-1]+f[i-2])%n; if(f[i] == f[2] && f[i-1] == f[1]){ record = i-2; break; } } int h = mod(a%record,b,record); printf("%d ",f[h]); } return 0; }