이 제출은 이전 버전의 oj.uz에서 채점하였습니다. 현재는 제출 당시와는 다른 서버에서 채점을 하기 때문에, 다시 제출하면 결과가 달라질 수도 있습니다.
#include <bits/stdc++.h>
#define ll long long
#define rep(i,m,n) for(int i=(m); i<=(n); i++)
#define reb(i,m,n) for(int i=(m); i>=(n); i--)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MP make_pair
#define fs first
#define se second
#define bit(msk, i) ((msk >> i) & 1)
#define iter(id, v) for(auto id : v)
#define pb push_back
#define SZ(v) (int)v.size()
#define ALL(v) v.begin(),v.end()
using namespace std;
mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }
const int N = 1e4 + 7;
const int Mod = 1e9 + 7;
const ll INF = 1e18 + 7;
const ll BASE = 137;
const int szBL = 320;
int n, m;
int a[2][N];
int dp[N][2 * N], f[N][2 * N];
ll sval[2 * N];
vector<int> vals = {0};
void solution () {
cin >> n;
rep (i, 1, n) cin >> a[0][i];
rep (i, 1, n) {
cin >> a[1][i];
if (a[1][i] <= a[0][i]) swap(a[1][i], a[0][i]);
vals.pb(a[1][i]);
vals.pb(a[0][i]);
}
sort (ALL(vals));
vals.resize(m = unique(ALL(vals)) - vals.begin());
rep (i, 1, n)
rep (k, 0, 1) a[k][i] = lower_bound(ALL(vals), a[k][i]) - vals.begin() + 1;
dp[0][1] = 1;
dp[0][1] = 1;
rep (i, 1, n) {
rep (k, 0, 1) {
rep (j, 1, m) {
if (j <= a[k][i]) {
(dp[i][a[k][i]] += dp[i - 1][j]) %= Mod;
}
else {
(dp[i][j] += dp[i - 1][j]) %= Mod;
}
}
}
}
f[n + 1][1] = 1;
f[n + 1][1] = 1;
reb (i, n, 1)
rep (k, 0, 1) {
rep (j, 1, m) {
if (j <= a[k][i]) {
(f[i][a[k][i]] += f[i + 1][j]) %= Mod;
}
else {
(f[i][j] += f[i + 1][j])%= Mod;
}
}
}
ll res = 0;
rep (i, 1, n) {
rep (k, 0, 1) {
// cout << i<<" "<<a[k][i] <<"\n";
sval[m + 1] = 0;
reb (j, m, a[k][i] + 1) {
sval[j] = (sval[j + 1] + f[i + 1][j]) % Mod;
}
rep (j, a[k][i] + 1, m) {
(res += 1LL * dp[i - 1][j] * sval[j] % Mod * (vals[j - 1] - vals[a[k][i] - 1]) % Mod) %= Mod;
// cout << i<<" "<<j<<" "<<p<<" "<<j<<" "<<a[k][i] <<" a\n";
}
sval[m + 1] = 0;
reb (j, m, a[k][i] + 1) {
sval[j] = (sval[j + 1] + dp[i - 1][j]) % Mod;
}
rep (j, a[k][i] + 1, m) {
(res += 1LL * f[i + 1][j] * sval[j + 1] % Mod * (vals[j - 1] - vals[a[k][i] - 1]) % Mod) %= Mod;
// cout << i<<" "<<j<<" "<<p<<" "<<j<<" "<<a[k][i] <<" a\n";
}
}
}
cout << res<<"\n";
}
#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
// file("c");
ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
int num_Test = 1;
// cin >> num_Test;
while (num_Test--)
solution();
}
/*
no bug challenge +4
mình có muốn dùng mảng này không?
2 + 8 * 2 - 9
4
1 1 1 1
2 2 2 2
*/
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