#include <bits/stdc++.h>
using namespace std;
const int N = 99;
long long n, f[N] = {0, 0, 2, 0, 4};
int main()
{
scanf("%lld", &n);
for (int i = 5; i <= n; ++i)
f[i] = f[i - 2] * 2;
printf("%lld", f[n]);
}
#include <bits/stdc++.h>
using namespace std;
const int N = 511;
char s[N][N];
int h, w, sh[N], sw[N], xh = -1, xw = -1, sa;
int main()
{
scanf("%d%d", &h, &w);
for (int i = 0; i < h; ++i)
{
scanf("%s", s[i]);
for (int j = 0; j < w; ++j)
if (s[i][j] == '*')
{
if (++sh[i] > 1)
{
if (xh >= 0 && xh != i)
return puts("NO"), 0;
xh = i;
}
if (++sw[j] > 1)
{
if (xw >= 0 && xw != j)
return puts("NO"), 0;
xw = j;
}
++sa;
}
}
if (xh < 0 || xw < 0 || sw[xw] + sh[xh] - 1 < sa)
return puts("NO"), 0;
int lh = xh, rh = xh, lw = xw, rw = xw;
while (lh >= 0 && s[lh][xw] == '*')
--lh;
while (rh < h && s[rh][xw] == '*')
++rh;
while (lw >= 0 && s[xh][lw] == '*')
--lw;
while (rw < w && s[xh][rw] == '*')
++rw;
if (++lh == xh || --rh == xh || ++lw == xw || --rw == xw)
return puts("NO"), 0;
puts(rh - lh + 1 == sw[xw] && rw - lw + 1 == sh[xh] ? "YES" : "NO");
}
好恶心的模拟啊。
#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 9;
char s[2 * N], las[N];
int n, st[N], num[N];
vector<pair<int, int>> fiv, sev;
unordered_map<int, unordered_map<char, int>> mp;
int main()
{
scanf("%d", &n);
for (int i = 0; i < n; ++i)
{
char *ss = s + st[i];
scanf("%s", ss);
st[i + 1] = ss + strlen(ss) + 1 - s;
for (int j = 0; ss[j]; ++j)
if (ss[j] == 'a' || ss[j] == 'e' || ss[j] == 'o' || ss[j] == 'i' || ss[j] == 'u')
{
++num[i];
las[i] = ss[j];
}
if (mp[num[i]].count(las[i]))
{
sev.emplace_back(mp[num[i]][las[i]], i);
mp[num[i]].erase(las[i]);
}
else
mp[num[i]][las[i]] = i;
}
for (unordered_map<int, unordered_map<char, int>>::iterator it = mp.begin(); it != mp.end(); ++it)
{
int pre = -1;
for (auto p : it->second)
{
if (pre < 0)
pre = p.second;
else
{
fiv.emplace_back(p.second, pre);
pre = -1;
}
}
}
while (sev.size() > fiv.size())
{
fiv.push_back(sev.back());
sev.pop_back();
}
printf("%d\n", sev.size());
while (!sev.empty())
{
printf("%s %s\n%s %s\n", s + st[fiv.back().first], s + st[sev.back().first], s + st[fiv.back().second], s + st[sev.back().second]);
sev.pop_back();
fiv.pop_back();
}
}
就差五分钟就打完了啊！！！早知道不看D了…
$f_{x} = c^{2x-6} \cdot f_{x-1} \cdot f_{x-2} \cdot f_{x-3}$，变形得
$c^x\cdot f_x=c^{x-1}\cdot f_{x-1}\cdot c^{x-2}\cdot f_{x-2}\cdot c^{x-3}\cdot f_{x-3}$
记$g(x)=\ln (c^x\cdot f_x)$，则$g(x)=g(x-1)+g(x-2)+g(x-3)=A\cdot g(1)+B\cdot g(2)+C\cdot g(3)$，其中A，B，C可以用矩阵快速幂在对数的时间内求出来。
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
struct Mod
{
const ll M, SM;
Mod(ll M) : M(M), SM(sqrt(M) + 0.5) {}
ll &qadd(ll &a, ll b) const { return a += b, a < M ? a : (a -= M); } //假如a和b都已经在同余系内，就不必取模了，取模运算耗时很高
ll add(ll a, ll b) const { return qadd(a = (a + b) % M, M); } //考虑a和b不在同余系内甚至为负数的情况
ll mul(ll a, ll b) const { return add(a * b, M); }
/*
ll mul(ll a, ll b) const //无循环快速计算同余乘法，根据a*b是否爆ll替换a*b%M，需要a<M且b<M，可以调用时手动取模
{
ll c = a / SM, d = b / SM;
a %= SM, b %= SM;
ll e = add(add(a * d, b * c), c * d / SM * (SM * SM - M));
return add(add(a * b, e % SM * SM), add(c * d % SM, e / SM) * (SM * SM - M));
}*/
ll pow(ll a, ll b) const
{
ll r = 1;
for (a = add(a, M); b; b >>= 1, a = mul(a, a))
if (b & 1)
r = mul(r, a);
return r;
}
ll inv(ll a) const { return pow(a, M - 2); } //要求M为素数
/*
ll inv(ll a) const //模m下a的乘法逆元，不存在返回-1（m为素数时a不为0必有逆元）
{
ll x, y, d = gcd(a, M, x, y);
return d == 1 ? add(x, M) : -1; //return pow(a, phi(M) - 1);
}
vector<ll> sol(ll a, ll b) const //解同余方程，返回ax=b(mod M)循环节内所有解
{
vector<ll> ans;
ll x, y, d = gcd(a, M, x, y);
if (b % d)
return ans;
ans.push_back(mul((b / d) % (M / d), x));
for (ll i = 1; i < d; ++i)
ans.push_back(add(ans.back(), M / d));
return ans;
}
*/
ll log(ll a, ll b) const
{
unordered_map<ll, ll> x;
for (ll i = 0, e = 1; i <= SM; ++i, e = mul(e, a))
if (!x.count(e))
x[e] = i;
for (ll i = 0, v = inv(pow(a, SM)); i <= SM; ++i, b = mul(b, v))
if (x.count(b))
return i * SM + x[b];
return -1;
}
} M(1e9 + 7), M1(1e9 + 6);
const int N = 5;
struct Matrix
{
static int n; //方阵代替矩阵
ll a[N][N];
Matrix(ll k = 0)
{
for (int i = 0; i < n; ++i)
fill(a[i], a[i] + n, 0), a[i][i] = k;
}
friend Matrix operator*(const Matrix &a, const Matrix &b)
{
Matrix r(0);
for (int i = 0; i < r.n; ++i)
for (int k = 0; k < r.n; ++k)
for (int j = 0; j < r.n; ++j)
M1.qadd(r.a[i][j], M1.mul(a.a[i][k], b.a[k][j]));
return r;
}
friend Matrix pow(Matrix a, ll b)
{
Matrix r(1);
for (; b; b >>= 1, a = a * a)
if (b & 1)
r = r * a;
return r;
}
} mat;
int Matrix::n = N;
ll n, f1, f2, f3, c;
int main()
{
scanf("%lld%lld%lld%lld%lld", &n, &f1, &f2, &f3, &c);
mat.a[0][0] = mat.a[0][1] = mat.a[0][2] = mat.a[0][3] = mat.a[0][4] = mat.a[1][0] = mat.a[2][1] = mat.a[3][3] = mat.a[3][4] = mat.a[4][4] = 1;
mat = pow(mat, n - 3);
c = M.pow(c * c, mat.a[0][4]);
c = M.mul(c, M.pow(f3, mat.a[0][0]));
c = M.mul(c, M.pow(f2, mat.a[0][1]));
c = M.mul(c, M.pow(f1, mat.a[0][2]));
printf("%lld\n", c);
}