#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int mod = 1e9 + 7;
ll qpow(ll b, ll p) {
ll ret = 1;
while(p) {
if(p & 1) ret = (ret * b) % mod;
b = (b * b) % mod, p >>= 1;
} return ret;
}
struct base {
ll x;
void fix() {
if(x < 0 or x >= mod) x %= mod;
if(x < 0) x += mod;
}
base() {x = 0;}
base(int _x) { x = _x; fix(); }
base(ll _x) { x = _x; fix(); }
base operator + (const base &o) const { return base(x + o.x); }
base operator - (const base &o) const { return base(x - o.x); }
base operator * (const base &o) const { return base(x * o.x); }
base operator / (const base &o) const {
return base(x * qpow(o.x, mod - 2)); }
friend istream& operator >> (istream &in, base &o) {
return in >> o.x; }
friend ostream& operator << (ostream &out, const base &o) {
return out << o.x; }
void operator += (const base &o) { (*this) = (*this) + o; }
void operator -= (const base &o) { (*this) = (*this) - o; }
void operator *= (const base &o) { (*this) = (*this) * o; }
void operator /= (const base &o) { (*this) = (*this) / o; }
};
const int maxn = 505;
base inv[maxn << 1];
base C[maxn][maxn];
base choose(int n, int r) {
if(r > n or r < 0 or n < 0) return 0;
base ret = 1;
for(int i = 1; i <= r; i++, n--) {
ret *= inv[i] * n;
} return ret;
}
int n;
int a[maxn], b[maxn];
int N_rng;
int l[maxn << 1], r[maxn << 1];
base dp[maxn << 1][maxn];
base BC[maxn << 1][maxn]; /* BC = nCr for big N = range size, [range][r] */
base SC[maxn][maxn]; /* SC = nCr for small N, all pair (N, R) */
base g[maxn << 1][maxn];
/* g[range][k] = \sum{i = 1}^{k} \binom{k - 1}{i - 1} * \binom{range_size}{i} */
int main(int argc, char const *argv[])
{
cin >> n;
vector<int> tmp;
for(int i = 1; i <= n; i++) {
cin >> a[i] >> b[i];
tmp.emplace_back(a[i]);
tmp.emplace_back(b[i]);
}
sort(tmp.begin(), tmp.end());
tmp.erase(unique(tmp.begin(), tmp.end()), tmp.end());
N_rng = 1;
l[1] = r[1] = tmp[0];
for(int i = 1; i < tmp.size(); i++) {
N_rng++;
l[N_rng] = tmp[i - 1] + 1;
r[N_rng] = tmp[i];
}
{ // precalc factorial^{-1}
inv[0] = 1;
for(int i = 1; i <= n; i++) {
inv[i] = inv[i - 1] / i;
}
}
{ // precalc C[][]
for(int i = 0; i <= n; i++) {
SC[i][0] = 1;
}
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= i; j++) {
SC[i][j] = SC[i - 1][j] + SC[i - 1][j - 1];
}
}
}
{ // precalc BC[][]
for(int i = 1; i <= N_rng; i++) {
for(int j = 0; j <= n; j++) {
int sz = r[i] - l[i] + 1;
if(sz < j) {
BC[i][j] = 0;
} else {
BC[i][j] = 1;
for(int k = 1; k <= j; k++, sz--) {
BC[i][j] *= inv[k] * sz;
}
}
}
}
}
{ // precalc g[][]
for(int range = 1; range <= N_rng; range++) {
for(int k = 1; k <= n; k++) {
for(int i = 1; i <= k; i++) {
g[range][k] += SC[k - 1][i - 1] * BC[range][i];
}
}
}
}
for(int i = 0; i <= N_rng; i++) {
dp[i][0] = 1;
}
for(int rng = 1; rng <= N_rng; rng++) {
for(int i = 1; i <= n; i++) {
dp[rng][i] = dp[rng - 1][i];
if(a[i] <= l[rng] and r[rng] <= b[i]) {
int cnt = 0;
for(int k = i; k >= 1; k--) {
if(a[i] <= l[rng] and r[rng] <= b[i]) {
cnt++;
}
dp[rng][i] += dp[rng - 1][k - 1] * g[rng][cnt];
}
}
}
}
base ans = 0;
for(int i = 1; i <= n; i++) {
ans += dp[N_rng][i];
}
cout << ans << endl;
return 0;
}
Compilation message
boat.cpp: In function 'int main(int, const char**)':
boat.cpp:78:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 1; i < tmp.size(); i++) {
~~^~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1265 ms |
16376 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1265 ms |
16376 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
38 ms |
16380 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1265 ms |
16376 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
