ZOJ-2105

递推关系，寻找循环段，然后找出其中规律输出下标

#include<cstdio>#include<vector>using namespace std;int main(){int A, B;size_t n;while (scanf("%d %d %d", &A, &B, &n), A || B || n){vector<int> arr;arr.push_back(1);arr.push_back(1);A %= 7;B %= 7;bool find = false;size_t i;while (!find){arr.push_back((A * arr[arr.size() - 1] + B * arr[arr.size() - 2]) % 7);for (i = 0; i < arr.size() - 2; i++)if (arr[i] == arr[arr.size() - 2]&& arr[i + 1] == arr[arr.size() - 1]){find = true;break;}}int period = arr.size() - 2 - i;if (n - 1 < i)printf("%d\n", arr[n - 1]);elseprintf("%d\n", arr[(n - 1 - i) % period + i]);}return 0;}