题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5950
题意：求解递推式f(n)=f(n-1)+2*f(n-2)+n^4。
写了个小东西，不过我的文章里式子是2*f(n-1)，内容差不多。凑合看
#include <bits/stdc++.h>
using namespace std; typedef long long LL;
const LL mod = ;
const int maxn = ;
LL n, a, b; typedef struct Matrix {
LL m[maxn][maxn];
int r;
int c;
Matrix() {
r = c = ;
memset(m, , sizeof(m));
}
} Matrix; Matrix mul(Matrix m1, Matrix m2) {
Matrix ans = Matrix();
ans.r = m1.r;
ans.c = m2.c;
for(int i = ; i <= m1.r; i++) {
for(int j = ; j <= m2.r; j++) {
for(int k = ; k <= m2.c; k++) {
if(m2.m[j][k] == ) continue;
ans.m[i][k] = ((ans.m[i][k] + m1.m[i][j] * m2.m[j][k] % mod) % mod) % mod;
}
}
}
return ans;
} Matrix quickmul(Matrix m, LL n) {
Matrix ans = Matrix();
for(int i = ; i <= m.r; i++) {
ans.m[i][i] = ;
}
ans.r = m.r;
ans.c = m.c;
while(n) {
if(n & ) {
ans = mul(m, ans);
}
m = mul(m, m);
n >>= ;
}
return ans;
} int main() {
// freopen("in", "r", stdin);
int T;
scanf("%d", &T);
while(T--) {
scanf("%I64d%I64d%I64d",&n,&a,&b);
if(n == ) {
printf("%I64d\n", a);
continue;
}
if(n == ) {
printf("%I64d\n", b);
continue;
} Matrix x; x.r = , x.c = ;
Matrix y; y.r = , y.c = ;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=;
x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=,x.m[][]=; y.m[][]=b,y.m[][]=a,y.m[][]=,y.m[][]=,y.m[][]=,y.m[][]=,y.m[][]=;
Matrix p = quickmul(x,n-);
Matrix ret = mul(p,y);
printf("%I64d\n", ret.m[][]);
// cout << ret.r << " " << ret.c << endl;
}
return ;
}