#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
using namespace std;
const int mxn=1500+5;
const int inf=1e9;
const ll mod = 1e9 + 7;
ll bigmod(ll a, ll b) {
if(b == 0) return 1;
int mid = b / 2;
ll res = bigmod(a, mid);
res = res * res % mod;
if(b % 2 == 1) return a * res % mod;
return res;
}
ll last[mxn][mxn] = {};
ll dp[mxn][mxn] = {};
ll sum[mxn][mxn] = {};
ll fact[mxn], inv[mxn];
ll pre[mxn][mxn] = {};
ll ncr(ll n, ll r) {
if(r > n) return 0;
ll res = fact[n];
res = res * inv[r] % mod;
res = res * inv[n - r] % mod;
return res;
}
int main() {
fact[0] = 1;
inv[0] = 1;
for(int i = 1; i < mxn; i++) {
fact[i] = fact[i - 1] * i % mod;
inv[i] = bigmod(fact[i], mod - 2) % mod;
}
int n;
cin >> n;
int a[n + 1], b[n + 1];
int l[n + 1] = {}, r[n + 1] = {};
vector<int> v;
v.push_back(0);
for(int i = 1; i <= n; i++) {
cin >> a[i] >> b[i];
v.push_back(a[i]);
v.push_back(a[i] - 1);
v.push_back(b[i]);
}
sort(v.begin(), v.end());
v.erase(unique(v.begin(), v.end()), v.end());
int len[v.size() + 2];
for(int i = 1; i < v.size(); i++) len[i] = v[i] - v[i - 1];
for(int i = 1; i < v.size(); i++) {
for(int j = 1; j <= n; j++) {
ll mul = 1;
ll tot = 0;
ll mul2 = 1;
for(int k = 1; k <= len[i]; k++) {
mul = mul * (len[i] - k + 1) % mod;
ll v1 = mul * inv[k] % mod;
ll v2 = mul2 * inv[k - 1] % mod;
// cout<<i<<" "<<j<<" "<<k<<endl;
// assert(ncr(j - 1, k - 1) == v2);
pre[i][j] += v2 * v1 % mod;
mul2 = mul2 * (j - k) % mod;
}
pre[i][j] %= mod;
}
}
for(int i = 1; i <= n; i++) {
l[i] = lower_bound(v.begin(), v.end(), a[i]) - v.begin();
r[i] = lower_bound(v.begin(), v.end(), b[i]) - v.begin();
}
dp[0][0] = 1;
for(int i = 0; i < v.size(); i++) sum[i][0] = 1;
ll ans = 0;
for(int p = 1; p <= n; p++) {
for(int i = l[p]; i <= r[p]; i++) {
ll tot = len[i];
ll found = 1;
for(int j = p - 1; j >= 0; j--) {
dp[i][j] = sum[i - 1][j] * pre[i][found] % mod;
sum[i][p] = (sum[i][p] + dp[i][j]) % mod;
if(l[j] <= i && i <= r[j]) found++;
}
}
for(int i = l[p]; i < v.size(); i++) sum[i][p] = (sum[i][p] + sum[i - 1][p]) % mod;
ans += sum[v.size() - 1][p];
}
cout<<ans % mod<<endl;
}
Compilation message
boat.cpp: In function 'int main()':
boat.cpp:59:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
59 | for(int i = 1; i < v.size(); i++) len[i] = v[i] - v[i - 1];
| ~~^~~~~~~~~~
boat.cpp:62:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
62 | for(int i = 1; i < v.size(); i++) {
| ~~^~~~~~~~~~
boat.cpp:66:7: warning: unused variable 'tot' [-Wunused-variable]
66 | ll tot = 0;
| ^~~
boat.cpp:98:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
98 | for(int i = 0; i < v.size(); i++) sum[i][0] = 1;
| ~~^~~~~~~~~~
boat.cpp:104:10: warning: unused variable 'tot' [-Wunused-variable]
104 | ll tot = len[i];
| ^~~
boat.cpp:121:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
121 | for(int i = l[p]; i < v.size(); i++) sum[i][p] = (sum[i][p] + sum[i - 1][p]) % mod;
| ~~^~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Execution timed out |
2076 ms |
348 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Execution timed out |
2076 ms |
348 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Runtime error |
65 ms |
508 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Execution timed out |
2076 ms |
348 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
