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mirror of https://git.sb/baoshuo/OI-codes.git synced 2024-11-08 14:18:47 +00:00

P6146 [USACO20FEB]Help Yourself G

https://www.luogu.com.cn/record/79815317
This commit is contained in:
Baoshuo Ren 2022-07-16 15:52:52 +08:00
parent 419289fb94
commit 7e7e4f27a1
Signed by: baoshuo
GPG Key ID: 00CB9680AB29F51A

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Luogu/P6146/P6146.cpp Normal file
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#include <iostream>
#include <algorithm>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e5 + 5;
const int mod = 1e9 + 7;
int n, s[N << 1], f[N];
std::pair<int, int> a[N];
int pow(int a, int b) {
int res = 1;
while (b) {
if (b & 1) res = 1ll * res * a % mod;
a = 1ll * a * a % mod;
b >>= 1;
}
return res;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i].first >> a[i].second;
s[a[i].second]++;
}
std::sort(a + 1, a + 1 + n);
for (int i = 1; i <= n << 1; i++) {
s[i] += s[i - 1];
}
for (int i = 1; i <= n; i++) {
f[i] = (f[i - 1] * 2 % mod + pow(2, s[a[i].first - 1]) % mod) % mod;
}
cout << f[n] << endl;
return 0;
}