// Om Namah Shivaya
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a, b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a, b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
*/
const int MOD = 1e9 + 7;
const int N = 500 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
ll fact[N], ifact[N];
ll bexp(ll a, ll b) {
a %= MOD;
if (a == 0) return 0;
ll res = 1;
while (b) {
if (b & 1) res = res * a % MOD;
a = a * a % MOD;
b >>= 1;
}
return res;
}
ll invmod(ll a) {
return bexp(a, MOD - 2);
}
ll ncr(ll n, ll r) {
if (n < 0 or r < 0 or n < r) return 0;
return fact[n] * ifact[r] % MOD * ifact[n - r] % MOD;
}
ll npr(ll n, ll r) {
if (n < 0 or r < 0 or n < r) return 0;
return fact[n] * ifact[n - r] % MOD;
}
void precalc(ll n) {
fact[0] = 1;
rep1(i, n) fact[i] = fact[i - 1] * i % MOD;
ifact[n] = invmod(fact[n]);
rev(i, n - 1, 0) ifact[i] = ifact[i + 1] * (i + 1) % MOD;
}
void solve(int test_case)
{
precalc(N-1);
ll n; cin >> n;
vector<pll> a(n+5);
rep1(i,n) cin >> a[i].ff >> a[i].ss;
vector<ll> b;
rep1(i,n) b.pb(a[i].ff), b.pb(a[i].ss);
sort(all(b));
b.resize(unique(all(b))-b.begin());
vector<pll> ranges;
ranges.pb({0,b[0]-1});
rep(i,sz(b)){
if(i+1 < sz(b)){
ranges.pb({b[i],b[i+1]-1});
}
else{
ranges.pb({b[i],b[i]});
}
}
ll m = sz(ranges);
ll choose[m+5][n+5];
memset(choose,0,sizeof choose);
rep(i,m){
auto [l,r] = ranges[i];
ll len = r-l+1;
choose[i][0] = 1;
ll curr = 1;
rep1(r,n){
if(len < r) break;
curr = curr * (len-r+1) % MOD;
choose[i][r] = curr * ifact[r] % MOD;
}
}
auto isect = [&](pll p1, pll p2){
return max(p1.ff,p2.ff) <= min(p1.ss,p2.ss);
};
ll choose_ways[m+5][n+5];
memset(choose_ways,0,sizeof choose_ways);
rep(i,m){
choose_ways[i][0] = 1;
choose_ways[i][1] = choose[i][1];
for(int j = 2; j <= n; ++j){
// endpoints fixed i.e 2 of these j guys are always chosen
// decide pick/ignore for rest j-2 guys
rep(more,j-2+1){
ll ways = ncr(j-2,more)*choose[i][more+2]%MOD;
choose_ways[i][j] += ways;
choose_ways[i][j] %= MOD;
}
}
}
// debug(ranges);
// debug(choose[2][1]);
ll dp[n+5][m+5];
memset(dp,0,sizeof dp);
rep(j,m+5) dp[0][j] = 1;
rep1(i,n){
dp[i][0] = 1;
rep1(j,m-1){
dp[i][j] = (dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1]+MOD)%MOD;
if(!isect(a[i],ranges[j])) conts;
dp[i][j] += choose[j][1]*dp[i-1][j-1];
dp[i][j] %= MOD;
ll good = 1;
rev(k,i-1,1){
// i and k fixed
// few more in between
if(isect(a[k],ranges[j])){
good++;
dp[i][j] += choose_ways[j][good]*dp[k-1][j-1];
dp[i][j] %= MOD;
// rep(more,good-2+1){
// ll choose_guys = ncr(good-2,more);
// ll choose_points = choose[j][more+2];
// ll choose_ways = choose_guys*choose_points % MOD;
// dp[i][j] += choose_ways*dp[k-1][j-1];
// dp[i][j] %= MOD;
// }
}
}
}
}
ll ans = (dp[n][m-1]-1+MOD)%MOD;
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
Compilation message
boat.cpp: In function 'void solve(int)':
boat.cpp:30:36: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
30 | #define rep(i, n) for(int i = 0; i < n; ++i)
| ^
boat.cpp:116:5: note: in expansion of macro 'rep'
116 | rep(i,sz(b)){
| ^~~
boat.cpp:117:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
117 | if(i+1 < sz(b)){
| ^
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
399 ms |
6260 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
399 ms |
6260 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
9 ms |
852 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
399 ms |
6260 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
