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OI-codes/LibreOJ/2880/2880.cpp

113 lines
2.2 KiB
C++

#include <iostream>
#include <algorithm>
#include <limits>
#include <utility>
#include <vector>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 2e5 + 5;
int n, c[N], st[N];
long long ans;
std::vector<int> xs;
std::pair<int, int> p[N];
inline int lowbit(int x) {
return x & -x;
}
void insert(int x, int y) {
for (; x; x -= lowbit(x)) c[x] = std::min(c[x], y);
}
int query(int x) {
int res = std::numeric_limits<int>::max();
for (; x <= n; x += lowbit(x)) res = std::min(res, c[x]);
return res;
}
void clear(int x) {
for (; x; x -= lowbit(x)) c[x] = std::numeric_limits<int>::max();
}
int search(int l, int r, int y) {
int res = r + 1;
while (l <= r) {
int mid = l + r >> 1;
if (p[st[mid]].second < y) {
res = mid;
r = mid - 1;
} else {
l = mid + 1;
}
}
return res;
}
void solve(int l, int r) {
if (l >= r) return;
int mid = (l + r) >> 1;
solve(l, mid);
solve(mid + 1, r);
for (int i = l, j = mid + 1, top = 0; i <= mid; i++) {
while (j <= r && p[j].second > p[i].second) {
while (top && p[st[top]].first > p[j].first) top--;
st[++top] = j++;
}
ans += top - search(1, top, query(p[i].first)) + 1;
insert(p[i].first, p[i].second);
}
for (int i = l; i <= mid; i++) {
clear(p[i].first);
}
std::sort(p + l, p + r + 1, [](const std::pair<int, int> &a, const std::pair<int, int> &b) {
return a.second > b.second;
});
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
std::fill_n(c, N, std::numeric_limits<int>::max());
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> p[i].first >> p[i].second;
xs.emplace_back(p[i].first);
}
std::sort(p + 1, p + 1 + n, [](const std::pair<int, int> &a, const std::pair<int, int> &b) {
return a.first < b.first;
});
std::sort(xs.begin(), xs.end());
xs.erase(std::unique(xs.begin(), xs.end()), xs.end());
for (int i = 1; i <= n; i++) {
p[i].first = std::lower_bound(xs.begin(), xs.end(), p[i].first) - xs.begin() + 1;
}
solve(1, n);
cout << ans << endl;
return 0;
}