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QOJ
ID | 题目 | 提交者 | 结果 | 用时 | 内存 | 语言 | 文件大小 | 提交时间 | 测评时间 |
---|---|---|---|---|---|---|---|---|---|
#329447 | #8209. Curly Palindromes | ckiseki# | WA | 8ms | 19232kb | C++20 | 2.8kb | 2024-02-16 19:06:50 | 2024-02-16 19:06:50 |
Judging History
answer
#include <bits/stdc++.h>
using namespace std;
#define all(x) begin(x), end(x)
#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
#include <experimental/iterator>
void debug_(auto s, auto ...a) {
cerr << "\e[1;32m(" << s << ") = (";
int f = 0;
(..., (cerr << (f++ ? ", " : "") << a));
cerr << ")\e[0m\n";
}
void orange_(auto s, auto L, auto R) {
cerr << "\e[1;33m[ " << s << " ] = [ ";
using namespace experimental;
copy(L, R, make_ostream_joiner(cerr, ", "));
cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif
using lld = int64_t;
const int mod = 1000000007;
int add(int a, int b) {
return a + b >= mod ? a + b - mod : a + b;
}
int sub(int a, int b) {
return a - b < 0 ? a - b + mod : a - b;
}
int mul(lld a, lld b) {
return static_cast<int>(a * b % mod);
}
const int maxn = 1000025;
int inv[maxn], fac[maxn], ifac[maxn];
int pinv2[maxn];
void init() {
inv[1] = 1;
fac[0] = ifac[0] = 1;
for (int i = 2; i < maxn; i++)
inv[i] = mul(inv[mod % i], mod - mod / i);
for (int i = 1; i < maxn; i++)
fac[i] = mul(fac[i - 1], i), ifac[i] = mul(ifac[i - 1], inv[i]);
pinv2[0] = 1;
for (int i = 1; i < maxn; i++)
pinv2[i] = mul(pinv2[i - 1], inv[2]);
}
int choose(int n, int k) {
if (k < 0 || n < k) return 0;
return mul(fac[n], mul(ifac[k], ifac[n - k]));
}
const int maxm = 2025;
int choose_k[maxm];
void init_k(int k) {
for (int i = 0; i < maxm; i++) {
choose_k[i] = 0;
}
int c = 1;
for (int i = 0; i <= k && i < maxm; i++) {
choose_k[i] = c;
c = mul(c, k - i);
c = mul(c, inv[i + 1]);
}
}
int gao(int a, int b) {
init_k(b);
int res = 0;
for (int i = 0; i <= a; i++) {
if ((a - i) % 2 == 0) {
res = add(res, mul(choose_k[i + (a - i) / 2], mul(choose(i + (a - i) / 2, i), mul(fac[a], pinv2[(a - i) / 2]))));
}
}
return res;
}
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
int n, m, k;
cin >> n >> m >> k;
init();
init_k(k);
vector<int> zzz(m + 1);
for (int i = 0; i <= m; i++)
zzz[i] = choose_k[i];
vector<int> pw(n + 1);
pw[0] = 1;
for (int i = 1; i <= n; i++)
pw[i] = mul(pw[i - 1], k);
int zero_border = gao(m, k);
int ans = 0;
for (int x = 1; x * 2 <= m; x++) {
int way = gao(m - x * 2, k - x);
way = mul(zzz[x], way);
zero_border = sub(zero_border, way);
int cur = 0;
for (int i = 0; ; i++) {
int rest = n - m - (m - x) * i;
if (rest < 0) break;
if (~i & 1) {
cur = add(cur, mul(rest + 1, pw[rest]));
} else {
cur = sub(cur, mul(rest + 1, pw[rest]));
}
}
ans = add(ans, mul(cur, way));
}
{
ans = add(ans, mul(zero_border, mul(n - m + 1, pw[n - m])));
}
cout << ans << '\n';
return 0;
}
詳細信息
Test #1:
score: 0
Wrong Answer
time: 8ms
memory: 19232kb
input:
4 0 0 o 1 1 c 2 2 p 3 3 c
output:
0
result:
wrong answer 1st lines differ - expected: '2', found: '0'