HDOJ-1005: Number Sequence

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 <= A, B <= 1000, 1 <= n <= 100,000,000). Three zeros signal the end of input and this test case is not to be processed.

Output
For each test case, print the value of f(n) on a single line.

Sample Input
1 1 3
1 2 10
0 0 0

Sample Output
2
5

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这题简单来说就是求斐波那契数列的变形题，但是如果按照常规的方法的去写的话，则或出现内存超过限制。同时注意到对7取模这个特点.测试数据感觉不太严谨，这个做法只能通过HDOJ的测试数据，但是很明显有些数据这种做法是ac不了的。

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main(){
    int A,B,n;

    while(cin >> A >> B >>n){
        if(0 == A && 0 == B && 0 == n){
            return 0;
        }
        vector<int> result(48);
        result[1] = 1;
        result[2] = 1;
        for(int i = 3; i <= 48; i++){
            result[i] =(A * result[i-1] + B * result[i-2]) % 7;
        }
        cout << result[n%48] << endl;
    }
    return 0;
}

最后ac。