#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define X first
#define Y second
const int maxn = 2e3 + 5;
const ll mod = 1e9 + 7;
int n,m;
int a[maxn], b[maxn];
vector<int> pos;
pii itv[maxn];
ll temp[maxn][maxn];
ll rec[maxn][maxn];
ll dp[maxn][maxn];
ll fac[maxn], invfac[maxn];
ll add(ll x, ll y) { return ((x+y)%mod + mod)%mod; }
ll mul(ll x, ll y) { return ((x*y)%mod + mod)%mod; }
ll inv(ll x, ll y) { return 1<x ? y - inv(y%x, x)*y/x : 1; }
ll combi1(ll x, ll y) {
return x<y ? 0 : mul(fac[x], mul(invfac[y], invfac[x-y]));
}
void init() {
//get interval
pos.push_back(0); pos.push_back(2e9);
for(int i=1;i<=n;i++) {
pos.push_back(a[i]);
pos.push_back(b[i]);
}
sort(pos.begin(),pos.end());
pos.erase(unique(pos.begin(),pos.end()),pos.end());
for(int i=0;i<pos.size();i++) {
if(i!=0 && pos[i-1]+1<=pos[i]-1) itv[++m] = {pos[i-1]+1,pos[i]-1};
itv[++m] = {pos[i],pos[i]};
}
// for(int i=1;i<=m;i++) printf("[%d, %d] ",itv[i].X,itv[i].Y);
// printf("\n");
//fac and invfac
fac[0] = 1; invfac[0] = inv(fac[0], mod);
// printf("fac %d = %lld inv = %lld\n",1,fac[1],invfac[1]);
for(int i=1;i<=m;i++) {
fac[i] = mul(fac[i-1], i);
invfac[i] = inv(fac[i], mod);
// printf("fac %d = %lld inv = %lld\n",i,fac[i],invfac[i]);
}
//precompute
for(int i=1;i<=m;i++) {
ll sz = itv[i].Y-itv[i].X+1;
temp[i][1] = sz;
for(int use=2;use<=n;use++) temp[i][use] = mul(temp[i][use-1], mul(sz-use+1, inv(use,mod)));
}
// printf("m = %d\n",m);
for(int i=1;i<=m/2;i++) {
for(int cnt=1;cnt<=n;cnt++) {
// if(cnt==1) printf("calc %d %d\n",i,cnt);
for(int use=1;use<=cnt;use++) rec[i][cnt] = add(rec[i][cnt], mul(temp[i][use], combi1(cnt-1,use-1)));
}
}
}
ll solve() {
ll res = 0;
for(int i=1;i<=m;i++) dp[0][i] = 1;
for(int i=1;i<=m;i++) {
for(int x=1;x<=n;x++) {
dp[x][i] = dp[x][i-1];
if(a[x]<=itv[i].X && itv[i].Y<=b[x]) {
ll cnt = 1;
for(int y=x-1;y>=0;y--) {
dp[x][i] = add(dp[x][i], mul(dp[y][i-1], rec[i][cnt]));
if(a[y]<=itv[i].X && itv[i].Y<=b[y]) cnt++;
}
}
// printf("dp %d %d = %lld\n",x,i,dp[x][i]);
}
}
for(int x=1;x<=n;x++) res = add(res, dp[x][m]);
return res;
}
int main() {
scanf("%d",&n);
for(int i=1;i<=n;i++) scanf("%d%d",&a[i],&b[i]);
init();
printf("%lld",solve());
}
Compilation message
boat.cpp: In function 'void init()':
boat.cpp:43:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i=0;i<pos.size();i++) {
^
boat.cpp: In function 'int main()':
boat.cpp:93:16: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d",&n);
^
boat.cpp:94:49: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
for(int i=1;i<=n;i++) scanf("%d%d",&a[i],&b[i]);
^
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1910 ms |
18476 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1910 ms |
18476 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
46 ms |
18476 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
1910 ms |
18476 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
