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| #include <deque>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
struct Point
{
int x, y;
Point(const int _x = 0, const int _y = 0): x(_x), y(_y) { }
bool operator<(const Point &rhs) const
{ return (x > rhs.x || (x == rhs.x && y > rhs.y)); }
bool operator==(const Point &rhs) const
{ return (x >= rhs.x && y > rhs.y); }
};
struct Decision
{
int left, right, index;
Decision(const int _left = 0, const int _right = 0, const int _index = 0):
left(_left), right(_right), index(_index) { }
};
vector<Point> a;
deque<Decision> Q;
int n;
long long f[50001];
inline long long W(const int j, const int i)
{ return f[j]+static_cast<long long>(a[i-1].x)*a[j].y; }
int Find(const Decision &d, const int i)
{
int left = d.left, right = d.right+1;
while (right-left > 1)
{
int mid = (left+right)>>1;
if (W(i, mid) < W(d.index, mid))
right = mid;
else
left = mid;
}
return left;
}
int main()
{
ios::sync_with_stdio(false);
cin >> n;
for (int i = 0, x, y; i != n; ++i)
{
cin >> x >> y;
a.push_back(Point(x, y));
}
sort(a.begin(), a.end());
n = unique(a.begin(), a.end())-a.begin();
a = vector<Point>(a.rbegin()+a.size()-n, a.rend());
f[0] = 0;
Q.push_back(Decision(1, n, 0));
for (int i = 1; i <= n; ++i)
{
f[i] = W(Q.front().index, i);
if (Q.front().left == Q.front().right)
Q.pop_front();
else
++Q.front().left;
while (!Q.empty())
{
if (W(i, Q.back().left) < W(Q.back().index, Q.back().left))
Q.pop_back();
else
{
Q.back().right = Find(Q.back(), i);
break;
}
}
if (Q.empty() || Q.back().right != n)
Q.push_back(Decision((Q.empty() ? i : Q.back().right)+1, n, i));
}
cout << f[n] << endl;
}
|
