#pragma GCC target("avx2")
#pragma GCC optimize("O3")
# include <x86intrin.h>
# include <bits/stdc++.h>
# include <ext/pb_ds/assoc_container.hpp>
# include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
template<typename T> using ordered_set = tree <T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define _USE_MATH_DEFINES_
#define ll long long
#define ld long double
#define Accepted 0
#define pb push_back
#define mp make_pair
#define sz(x) (int)(x.size())
#define every(x) x.begin(),x.end()
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define For(i,x,y) for (ll i = x; i <= y; i ++)
#define FOr(i,x,y) for (ll i = x; i >= y; i --)
#define SpeedForce ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
// ROAD to... Red
inline void Input_Output () {
//freopen(".in", "r", stdin);
//freopen(".out", "w", stdout);
}
const double eps = 0.000001;
const ld pi = acos(-1);
const int maxn = 1e7 + 9;
const int mod = 1e9 + 7;
const ll MOD = 1e18 + 9;
const ll INF = 1e18 + 123;
const int inf = 2e9 + 11;
const int mxn = 1e6 + 9;
const int N = 6e5 + 123;
const int M = 22;
const int pri = 997;
const int Magic = 2101;
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};
int n;
ll dp[505][1010];
ll p[1001][1010];
int C1[1001][1001];
int C2[1001][1001];
int l[505], r[505];
int vv[N], ptr;
ll inv[N];
ll pw[N];
ll bpow (ll a, ll b) {
ll res = 1;
while (b > 0) {
if (b & 1) (res *= a) %= mod;
(a *= a) %= mod;
b /= 2;
}
return res;
}
ll C(ll n, int k) {
ll res = inv[k];
for (int i = 0; i < k; ++i) {
res *= (n - i);
res %= mod;
}
return res;
}
int main () {
SpeedForce;
inv[0] = 1;
pw[0] = 1;
for (int i = 1; i < 1001;i ++) {
inv[i] = inv[i-1] * bpow(i, mod - 2) % mod;
pw[i] = (pw[i-1] + pw[i-1]) % mod;
}
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> l[i] >> r[i];
r[i]++;
vv[ptr++] = l[i];
vv[ptr++] = r[i];
}
sort(vv, vv + ptr);
ptr = unique(vv, vv + ptr) - vv;
for (int i = 0; i < ptr; ++i) dp[0][i] = 1;
for (int i = 1; i < ptr; ++i) {
for (int j = 1; j <= n; ++j)
C2[i][j] = C(vv[i] - vv[i-1], j);
}
for (int i = 0; i <= n; ++i)
C1[i][i] = C1[i][0] = 1;
for (int i = 1; i <= n; ++i) {
for (int j = 1; j < i; ++j)
C1[i][j] = (C1[i-1][j] + C1[i-1][j-1]) % mod;
}
for (int i = 1; i < ptr; ++i) {
for (int k = 1; k <= n; ++k) {
for (int j = 1; j <= k; ++j)
p[i][k] = (p[i][k] + C2[i][j] * (ll)C1[k-1][j-1]) % mod;
}
}
for (int i = 0; i < ptr; ++i)
dp[0][i] = 1;
for (int i = 0; i <= n; ++i)
dp[i][0] = 1;
for (int i = 1; i <= n; ++i) {
for (int j = 1; j < ptr; ++j) {
dp[i][j] = dp[i][j-1];
int cnt = 0;
for (int k = i; k>=1; --k) {
if (l[k] <= vv[j-1] && vv[j] <= r[k]) {
++cnt;
dp[i][j] = (dp[i][j] + dp[k-1][j-1] * p[j][cnt]) % mod;
if (!p[j][nct]) break;
}
}
}
}
int ans = (dp[n][ptr-1] - 1 + mod) % mod;
assert(ans >= 0);
cout << ans << '\n';
return Accepted;
}
// B...a
Compilation message
fireworks.cpp: In function 'int main()':
fireworks.cpp:140:16: error: 'nct' was not declared in this scope
if (!p[j][nct]) break;
^~~
