cp/codeforces/918/f.cc
2025-08-26 14:13:02 -05:00

114 lines
2.3 KiB
C++

#include <bits/stdc++.h> // {{{
// https://codeforces.com/blog/entry/96344
#pragma GCC optimize("O2,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
using f64 = double;
using f128 = long double;
#if __cplusplus >= 202002L
template <typename T>
constexpr T MIN = std::numeric_limits<T>::min();
template <typename T>
constexpr T MAX = std::numeric_limits<T>::max();
template <typename T>
[[nodiscard]] static T sc(auto&& x) {
return static_cast<T>(x);
}
template <typename T>
[[nodiscard]] static T sz(auto&& x) {
return static_cast<T>(x.size());
}
#endif
static void NO() {
std::cout << "NO\n";
}
static void YES() {
std::cout << "YES\n";
}
template <typename T>
using vec = std::vector<T>;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define ff first
#define ss second
#ifdef LOCAL
#define db(...) std::print(__VA_ARGS__)
#define dbln(...) std::println(__VA_ARGS__)
#else
#define db(...)
#define dbln(...)
#endif
// }}}
i64 inv_merge(vector<i64>& a, vector<i64>& tmp) {
if (r - l <= 1)
return 0;
int m = (l + r) >> 1;
i64 ans = inv_merge(a, tmp, l, m) + inv_merge(a, tmp, m, r);
int i = l, j = m, k = l;
while (i < m || j < r) {
if (j == r || (i < m && a[i] <= a[j]))
tmp[k++] = a[i++];
else {
tmp[k++] = a[j++];
ans += (m - i);
}
}
return ans;
}
void solve() {
// NOTE: erroneosouyl thought was interval overlaps (even that took too long
// to code) should've stayed at it and continued, but was tired/acted tired
// consider the problem statemnt & examples more slowly
// simplifcation: count the inversions
i32 n;
cin >> n;
vector<pair<i64, i64>> p(n);
for (i32 i = 0; i < n; ++i)
cin >> p[i].first >> p[i].second;
sort(all(p));
vector<i64> b(n), tmp(n);
for (i32 i = 0; i < n; ++i)
b[i] = p[i].second;
println("{}", inv_merge(b, tmp, 0, n));
}
int main() { // {{{
std::cin.exceptions(std::cin.failbit);
#ifdef LOCAL
std::cerr.rdbuf(std::cout.rdbuf());
std::cout.setf(std::ios::unitbuf);
std::cerr.setf(std::ios::unitbuf);
#else
std::cin.tie(nullptr)->sync_with_stdio(false);
#endif
u32 tc = 1;
std::cin >> tc;
for (u32 t = 0; t < tc; ++t) {
solve();
}
return 0;
}
// }}}