【BestCoder】 HDOJ 5171 GTY's birthday gift

矩阵快速幂。。。。构造矩阵的方法有很多种，任选一种即可。。。

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 405
#define maxm 400005
#define eps 1e-7
#define mod 10000007
#define INF 999999999
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R
#define pii pair<int, int>
#pragma comment(linker, "/STACK:16777216")
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
// head

LL mat[10][10];
LL res[10][10];
LL mid[10][10];
int n, k;

LL cal(int c)
{
    memset(res, 0, sizeof res);
    memset(mat, 0, sizeof mat);
    res[1][1] = res[2][2] = res[3][3] = res[4][4] = 1;
    mat[1][1] = mat[1][2] = mat[2][1] = 1;
    mat[2][2] = 0;
    mat[1][3] = mat[1][4] = mat[2][3] = 1;
    mat[2][4] = 0;
    mat[3][3] = mat[4][4] = 1;
    while(c) {
        if(c % 2) {
            for(int i = 1; i <= 4; i++)
                for(int j = 1;  j <= 4; j++) {
                    LL t = 0;
                    for(int k = 1; k <= 4; k++)
                        t = (t + res[i][k] * mat[k][j]) % mod;
                    mid[i][j] = t;
                }
            for(int i = 1; i <= 4; i++)
                for(int j = 1; j <= 4; j++)
                    res[i][j] = mid[i][j];
        }
        for(int i = 1; i <= 4; i++)
            for(int j = 1; j <= 4; j++) {
                LL t = 0;
                for(int k = 1; k <= 4; k++)
                    t = (t + mat[i][k] * mat[k][j]) % mod;
                mid[i][j] = t;
            }
        for(int i = 1; i <= 4; i++)
            for(int j = 1; j <= 4; j++)
                mat[i][j] = mid[i][j];
        c /= 2;
    }
    return res[1][4];
}

void work()
{
    LL a, b, x;
    scanf("%I64d%I64d", &a, &b);
    if(a < b) swap(a, b);
    LL res = (a + b) % mod;
    for(int i = 3; i <= n; i++) {
        scanf("%I64d", &x);
        if(x >= a) b = a, a = x;
        else b = max(b, x);
        res = (res + x) % mod;
    }
    res = (res + a * (cal(k + 1) - 1 + mod) % mod + b * cal(k) % mod) % mod;
    printf("%I64d\n", res);

}

int main()
{
    //for(int i = 1; i <= 10; i++) printf("AAAAA %lld\n", cal(i));
    while(scanf("%d%d", &n, &k)!=EOF) {
        work();
    }
    
    
    return 0;
}