#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod=1e9+7;
ll n,c[1001],st[501],ed[501],cnt,comb[501];
ll dp[501][1001];
set<int> ss;
ll power(int a, int m) { //a^m;
ll ans=1;
while (m) {
if (m%2==1) ans=(ans*a)%mod;
a=(a*a)%mod;
m/=2;
}
return ans;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin>>n;
for (int i=1; i<=n; ++i) {
cin>>st[i]>>ed[i]; --st[i];
ss.insert(st[i]);
ss.insert(ed[i]);
}
for (int i=1; i<=n; ++i) comb[i]=power(i,mod-2);
cnt=ss.size()-1;
int id=0;
for (auto it=ss.begin(); it!=ss.end(); ++it) c[id++]=*it;
for (int i=0; i<=cnt; ++i) dp[0][i]=1;
for (int i=1; i<=n; ++i) {
dp[i][0]=1; //don't send any boat
for (int j=1; j<=cnt; ++j) { //consider from the range from c[j-1]+1 to c[j]
dp[i][j]=dp[i][j-1];
ll idx=1,com=1;
for (auto k=i; k>0; --k) {
if (st[k]<c[j] && c[j]<=ed[k]) {
com=((com*(c[j]-c[j-1]+idx-1)%mod)*comb[idx])%mod;
dp[i][j]=(dp[i][j]+dp[k-1][j-1]*com)%mod;
++idx;
}
}
}
}
cout<<(dp[n][cnt]-1+mod)%mod;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
226 ms |
4248 KB |
Output is correct |
2 |
Correct |
224 ms |
4196 KB |
Output is correct |
3 |
Correct |
225 ms |
4228 KB |
Output is correct |
4 |
Correct |
219 ms |
4248 KB |
Output is correct |
5 |
Correct |
222 ms |
4296 KB |
Output is correct |
6 |
Correct |
130 ms |
4304 KB |
Output is correct |
7 |
Correct |
130 ms |
4300 KB |
Output is correct |
8 |
Correct |
127 ms |
4224 KB |
Output is correct |
9 |
Correct |
131 ms |
4172 KB |
Output is correct |
10 |
Correct |
133 ms |
4280 KB |
Output is correct |
11 |
Correct |
133 ms |
4268 KB |
Output is correct |
12 |
Correct |
134 ms |
4244 KB |
Output is correct |
13 |
Correct |
125 ms |
4300 KB |
Output is correct |
14 |
Correct |
119 ms |
4192 KB |
Output is correct |
15 |
Correct |
129 ms |
4272 KB |
Output is correct |
16 |
Incorrect |
47 ms |
2948 KB |
Output isn't correct |
17 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
226 ms |
4248 KB |
Output is correct |
2 |
Correct |
224 ms |
4196 KB |
Output is correct |
3 |
Correct |
225 ms |
4228 KB |
Output is correct |
4 |
Correct |
219 ms |
4248 KB |
Output is correct |
5 |
Correct |
222 ms |
4296 KB |
Output is correct |
6 |
Correct |
130 ms |
4304 KB |
Output is correct |
7 |
Correct |
130 ms |
4300 KB |
Output is correct |
8 |
Correct |
127 ms |
4224 KB |
Output is correct |
9 |
Correct |
131 ms |
4172 KB |
Output is correct |
10 |
Correct |
133 ms |
4280 KB |
Output is correct |
11 |
Correct |
133 ms |
4268 KB |
Output is correct |
12 |
Correct |
134 ms |
4244 KB |
Output is correct |
13 |
Correct |
125 ms |
4300 KB |
Output is correct |
14 |
Correct |
119 ms |
4192 KB |
Output is correct |
15 |
Correct |
129 ms |
4272 KB |
Output is correct |
16 |
Incorrect |
47 ms |
2948 KB |
Output isn't correct |
17 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
5 ms |
852 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
226 ms |
4248 KB |
Output is correct |
2 |
Correct |
224 ms |
4196 KB |
Output is correct |
3 |
Correct |
225 ms |
4228 KB |
Output is correct |
4 |
Correct |
219 ms |
4248 KB |
Output is correct |
5 |
Correct |
222 ms |
4296 KB |
Output is correct |
6 |
Correct |
130 ms |
4304 KB |
Output is correct |
7 |
Correct |
130 ms |
4300 KB |
Output is correct |
8 |
Correct |
127 ms |
4224 KB |
Output is correct |
9 |
Correct |
131 ms |
4172 KB |
Output is correct |
10 |
Correct |
133 ms |
4280 KB |
Output is correct |
11 |
Correct |
133 ms |
4268 KB |
Output is correct |
12 |
Correct |
134 ms |
4244 KB |
Output is correct |
13 |
Correct |
125 ms |
4300 KB |
Output is correct |
14 |
Correct |
119 ms |
4192 KB |
Output is correct |
15 |
Correct |
129 ms |
4272 KB |
Output is correct |
16 |
Incorrect |
47 ms |
2948 KB |
Output isn't correct |
17 |
Halted |
0 ms |
0 KB |
- |