HDU2256-Problem of precision (matrix construction + Rapid power)

Question Link

Question: SQRT (2) + SQRT (3) ^ 2n mod 1024

Ideas:

Code:

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const int MOD = 1024;int n;struct mat {    int s[2][2];    mat(int a = 0, int b = 0, int c = 0, int d = 0) {        s[0][0] = a;         s[0][1] = b;         s[1][0] = c;         s[1][1] = d;     }    mat operator * (const mat& c) {        mat ans;         sizeof(ans.s, 0, sizeof(ans.s));        for (int i = 0; i < 2; i++)             for (int j = 0; j < 2; j++)                for (int k = 0; k < 2; k++)                    ans.s[i][j] = (ans.s[i][j] + s[i][k] * c.s[k][j]) % MOD;        return ans;    }}tmp(5, 12, 2, 5);mat pow_mod(int k) {    if (k == 1)        return tmp;    mat a = pow_mod(k / 2);    mat ans = a * a;    if (k % 2)        ans = ans * tmp;    return ans;}int main() {    int cas;    scanf("%d", &cas);    while (cas--) {        scanf("%d", &n);         mat ans = pow_mod(n);         printf("%d\n", (ans.s[0][0] * 2 - 1) % MOD);     }    return 0;}

HDU2256-Problem of precision (matrix construction + Rapid power)