78 lines
1.7 KiB
C++
78 lines
1.7 KiB
C++
#include<stdio.h>
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#include<string.h>
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#include<algorithm>
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using namespace std;
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#define LL _int64
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#define mod 10000007
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int a[100010];
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struct matrix
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{
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LL m[3][3];
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};
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matrix mul(matrix x, matrix y)
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{
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matrix temp;
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memset(temp.m, 0, sizeof(temp.m));
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int i, j, k;
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for (i = 0; i < 3; i++)
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{
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for (j = 0; j < 3; j++)
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{
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if (x.m[i][j] == 0)
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{
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continue;
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}
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for (k = 0; k < 3; k++)
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{
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if (y.m[j][k] == 0)
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{
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continue;
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}
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temp.m[i][k] = (temp.m[i][k] + (x.m[i][j] * y.m[j][k]) % mod) % mod;
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}
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}
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}
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return temp;
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}
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matrix quickpow(matrix a, int n)
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{
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matrix res;
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int i;
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memset(res.m, 0, sizeof(res.m));
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for (i = 0; i < 3; i++)
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{
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res.m[i][i] = 1;
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}
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while (n)
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{
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if (n & 1)
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{
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res = mul(res,a);
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}
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n >>= 1;
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a = mul(a, a);
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}
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return res;
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}
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int main()
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{
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int n, k;
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while ((scanf("%d%d", &n, &k)) != EOF)
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{
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LL sum = 0;
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for (int i = 0; i < n; i++)
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{
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scanf("%d", &a[i]);
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sum += a[i];
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}
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sort(a, a + n);
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matrix ans;
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ans.m[0][0] = 1; ans.m[0][1] = 1; ans.m[0][2] = 1;
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ans.m[1][0] = 0; ans.m[1][1] = 1; ans.m[1][2] = 1;
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ans.m[2][0] = 0; ans.m[2][1] = 1; ans.m[2][2] = 0;
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ans = quickpow(ans, k);
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printf("%d\n", (ans.m[0][0] * sum + ans.m[0][1] * a[n - 1] + ans.m[0][2] * a[n - 2]) % mod);
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}
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return 0;
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}
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