A Simple Math Problem
針對該問題的形式是線性組合,因此可以考慮矩陣相乘的算法。
#pragma warning(disable:4996)
#include<iostream>
using namespace std;
long k, mod;
struct Matrix {
int m[12][12];
};
Matrix factors;
void init()
{
memset(factors.m, 0, sizeof(factors.m));
for (int i = 0; i<9; i++)
factors.m[i][i+1] = 1;
}
//兩個矩陣相乘
Matrix multiply(Matrix a, Matrix b)
{
Matrix result;
memset(result.m, 0, sizeof(result.m));
for (int i = 0; i < 10; i++)
{
for (int j = 0; j < 10; j++)
{
for (int k = 0; k < 10; k++)
result.m[i][j] = (result.m[i][j] + a.m[i][k] * b.m[k][j]) % mod;
result.m[i][j] %= mod;
}
}
return result;
}
//獲取矩陣的n次方,很重要
Matrix getPow(Matrix a,Matrix b, int n)
{
while(n)
{?
if (n & 1) b = multiply(a, b);
n >>= 1;
a = multiply(a, a);
}
return b;
}
int main()
{
//freopen("a.txt", "r", stdin);
while (cin >> k >> mod)
{
init();
for (int i = 0; i < 10; i++)
{
cin >> factors.m[i][0];
}
if (k<10) {
cout << k%mod << endl;
continue;
}
Matrix t;
memset(t.m, 0, sizeof(t.m));
for(int j = 0; j< 10; j++)
t.m[j][j] = 1;
Matrix re = getPow(factors, t, k - 9);
long result = 0;
for (int j = 0; j < 10; j++)
{
result += (re.m[j][0] * (9-j)) % mod;
}
cout << result%mod<< endl;
}
return 0;
}
總結
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