#include <algorithm>
#include <iostream>
#include <iomanip>
#include <bitset>
#include <cmath>
#include <queue>
#include <map>
#include <set>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define ent "\n"
const int maxn = 5e2 + 100;
const ll INF = (1ll<<61);
const int MOD = 1e9 + 7;
const int inf = (1<<30);
const int maxl = 20;
const int P = 31;
int n;
int a[maxn];
int b[maxn];
ll dp[maxn][maxn * 2];
int cal[maxn];
ll f[maxn * 2][maxn];
ll br[maxn];
ll cnk[maxn][maxn];
vector<int> v;
ll fc[maxn];
ll binpow(ll a, ll b){
if(!b) return 1;
ll num = binpow(a, b >> 1);
num = num * num % MOD;
if(b & 1) num = num * a % MOD;
return num;
}
int c(int n, int k){
if(k > n) return 0;
ll ans = 1;
for(int i = n - k + 1; i <= n; i++){
ans = (ans * i) % MOD;
}
for(int i = 1; i <= k; i++){
ans = (ans * br[i]) % MOD;
}
return ans;
}
bool ok(int i, int j){
return v[j] >= a[i] && v[j+1] - 1 <= b[i];
}
void test(){
cin >> n;
for(int i = 1; i <= n; i++){
cin >> a[i] >> b[i];
v.push_back(a[i]);
v.push_back(b[i] + 1);
br[i] = binpow(i, MOD - 2);
}
v.push_back(1e9 + 1);
sort(v.begin(), v.end());
v.resize(unique(v.begin(), v.end()) - v.begin());
int ans = 0;
cnk[0][0] = 1;
for(int i = 1; i <= n; i++){
for(int j = 0; j <= i; j++){
cnk[i][j] = cnk[i-1][j];
if(j) cnk[i][j] = (cnk[i][j] + cnk[i-1][j-1]) % MOD;
}
}
for(int i = 0; i < v.size() - 1; i++){
for(int j = 0; j <= n; j++){
fc[j] = c(v[i+1] - v[i], j);
}
for(int j = n; j >= 0; j--){
for(int k = j; k <= n; k++){
f[i][k] = (f[i][k] + 1ll * cnk[k-1][j-1] * fc[j]) % MOD;
}
}
}
for(int i = 1; i <= n; i++){
for(int k = i - 1; k > 0; k--){
for(int j = 0; j < v.size() - 1; j++){
if(ok(k+1, j)) cal[j]++;
if(j) dp[i][j] = (dp[i][j] + 1ll * dp[k][j-1] * f[j][cal[j]]) % MOD;
}
}
for(int j = 0; j < v.size() - 1; j++){
dp[i][j] = (dp[i][j] + f[j][cal[j]]) % MOD;
if(!ok(i, j)) dp[i][j] = 0;
ans = (ans + dp[i][j]) % MOD;
if(j) dp[i][j] = (dp[i][j] + dp[i][j-1]) % MOD;
}
}
cout << ans << ent;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int t; t = 1;
while(t--) test();
}
Compilation message
boat.cpp: In function 'void test()':
boat.cpp:77:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
77 | for(int i = 0; i < v.size() - 1; i++){
| ~~^~~~~~~~~~~~~~
boat.cpp:89:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
89 | for(int j = 0; j < v.size() - 1; j++){
| ~~^~~~~~~~~~~~~~
boat.cpp:94:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
94 | for(int j = 0; j < v.size() - 1; j++){
| ~~^~~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
1288 ms |
12028 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
1288 ms |
12028 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
16 ms |
2180 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
1288 ms |
12028 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |