#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace std;
using namespace __gnu_pbds;
template <typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// find_by_order(k) -> iterator of kth element (in sorted fashion : low - high)
// order_of_key(x) -> #numbers strictly less than x
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define sync ios_base::sync_with_stdio(0); cin.tie(0);
#define all(x) x.begin(),x.end()
#define unq(a) sort(all(a));a.resize(unique(all(a)) - a.begin())
#define fi first
#define se second
#define endl '\n'
using ll = long long
;using ld = long double;
using pii = pair<int , int>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//mt19937 rng(0);
const int mod = 1e9 + 7;
template <typename T>
class Modular {
public:
using Type = typename decay<decltype(T::value)>::type;
constexpr Modular() : value() {}
template <typename U>
Modular(const U& x) {
value = normalize(x);
}
template <typename U>
static Type normalize(const U& x) {
Type v;
if (-mod() <= x && x < mod()) v = static_cast<Type>(x);
else v = static_cast<Type>(x % mod());
if (v < 0) v += mod();
return v;
}
const Type& operator()() const { return value; }
template <typename U>
explicit operator U() const { return static_cast<U>(value); }
constexpr static Type mod() { return T::value; }
Modular& operator+=(const Modular& other) { if ((value += other.value) >= mod()) value -= mod(); return *this; }
Modular& operator-=(const Modular& other) { if ((value -= other.value) < 0) value += mod(); return *this; }
template <typename U> Modular& operator+=(const U& other) { return *this += Modular(other); }
template <typename U> Modular& operator-=(const U& other) { return *this -= Modular(other); }
Modular& operator++() { return *this += 1; }
Modular& operator--() { return *this -= 1; }
Modular operator++(int) { Modular result(*this); *this += 1; return result; }
Modular operator--(int) { Modular result(*this); *this -= 1; return result; }
Modular operator-() const { return Modular(-value); }
template <typename U = T>
typename enable_if<is_same<typename Modular<U>::Type, int>::value, Modular>::type& operator*=(const Modular& rhs) {
value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
return *this;
}
template <typename U = T>
typename enable_if<is_same<typename Modular<U>::Type, int64_t>::value, Modular>::type& operator*=(const Modular& rhs) {
int64_t q = static_cast<int64_t>(static_cast<long double>(value) * rhs.value / mod());
value = normalize(value * rhs.value - q * mod());
return *this;
}
template <typename U = T>
typename enable_if<!is_integral<typename Modular<U>::Type>::value, Modular>::type& operator*=(const Modular& rhs) {
value = normalize(value * rhs.value);
return *this;
}
Modular inverse() const {
Type a = value, b = mod(), u = 0, v = 1;
while (a != 0) {
Type t = b / a;
b -= t * a; swap(a, b);
u -= t * v; swap(u, v);
}
assert(b == 1);
return Modular(u);
}
Modular& operator/=(const Modular& other) { return *this *= other.inverse(); }
template <typename U>
friend bool operator==(const Modular<U>& lhs, const Modular<U>& rhs);
template <typename U>
friend std::istream& operator>>(std::istream& stream, Modular<U>& number);
private:
Type value;
};
template <typename T> bool operator==(const Modular<T>& lhs, const Modular<T>& rhs) { return lhs.value == rhs.value; }
template <typename T, typename U> bool operator==(const Modular<T>& lhs, U rhs) { return lhs == Modular<T>(rhs); }
template <typename T, typename U> bool operator==(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) == rhs; }
template <typename T> bool operator!=(const Modular<T>& lhs, const Modular<T>& rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(const Modular<T>& lhs, U rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(U lhs, const Modular<T>& rhs) { return !(lhs == rhs); }
template <typename T> Modular<T> operator+(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }
template <typename T> Modular<T> operator-(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T> Modular<T> operator*(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T> Modular<T> operator/(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }
template<typename T, typename U>
Modular<T> power(const Modular<T>& a, const U& b) {
assert(b >= 0);
Modular<T> x = a, res = 1;
U p = b;
while (p > 0) {
if (p & 1) res *= x;
x *= x;
p >>= 1;
}
return res;
}
template <typename T>
string to_string(const Modular<T>& number) {
return to_string(number());
}
template <typename T>
std::ostream& operator<<(std::ostream& stream, const Modular<T>& number) {
return stream << number();
}
template <typename T>
std::istream& operator>>(std::istream& stream, Modular<T>& number) {
stream >> number.value;
number.value = Modular<T>::normalize(number.value);
return stream;
}
struct VarMod { static int value; };
int VarMod::value;
using mint = Modular<std::integral_constant<int, mod>>;
int main(){
sync
//#ifndef ONLINE_JUDGE
freopen("kangaroo.in", "r", stdin);
freopen("kangaroo.out", "w", stdout);
//#endif
int tt = 1;
//cin >> tt;
while(tt--){
int n, s, e;
cin >> n >> s >> e;
vector<vector<vector<mint>>> dp(n + 1, vector<vector<mint>>(n + 1, vector<mint>(4)));
for (int i = 0; i <= n; i++){
if (i){
if (i == s or i == e){
dp[i] = dp[i - 1];
continue;
}
for (int pc = 2; pc <= n - 1; pc++){
for (int msk = 0; msk < 4; msk++){
//merge edge
if (pc != 2){
int l = ((msk >> 1) ? 1 : (i > s));
if (l)
dp[i][pc - 1][msk | 2] += dp[i - 1][pc][msk];
int r = ((msk & 1) ? 1 : (i > e));
if (r)
dp[i][pc - 1][msk | 1] += dp[i - 1][pc][msk];
}
else{
int l = ((msk >> 1) ? 1 : (i > s));
int r = ((msk & 1) ? 1 : (i > e));
if (l && r){
dp[i][pc - 1][3] += dp[i - 1][pc][msk];
}
}
// merge inside component
dp[i][pc - 1][msk] += (max(0, (pc - 3)) * dp[i - 1][pc][msk]);
// append only possible for edge components
if (i < s && 1 - (msk >> 1)){
dp[i][pc][msk | 2] += dp[i - 1][pc][msk];
}
if (i < e && 1 - (msk & 1)){
dp[i][pc][msk | 1] += dp[i - 1][pc][msk];
}
// new component
dp[i][pc + 1][msk] += ((pc - 1) * dp[i - 1][pc][msk]);
}
}
}
else{
if (n == 2) dp[0][1][3] = 1;
else dp[0][2][0] = 1;
}
}
// for (int i = 1; i <= n; i++){
// for (int j = 1; j <= n; j++){
// for (int msk = 0; msk < 4; msk++){
// cout << i << " " << j << " " << bitset<2>(msk) << " " << dp[i][j][msk] << endl;
// }
// }
// }
cout << dp[n][1][3] << endl;
}
cerr << "processor time: " << clock() / (double) CLOCKS_PER_SEC << "s ";
return 0;
}
Compilation message
kangaroo.cpp: In function 'int main()':
kangaroo.cpp:165:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
165 | freopen("kangaroo.in", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:166:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
166 | freopen("kangaroo.out", "w", stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2 ms |
588 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2 ms |
588 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2 ms |
588 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2 ms |
588 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
