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it unlocks many cool features!
- const ll is_query = -(1LL << 62);
- struct Line {
- ll m, b;
- mutable function<const Line *()> succ;
- bool operator<(const Line &rhs) const {
- if (rhs.b != is_query) return m < rhs.m;
- const Line *s = succ();
- if (!s) return 0;
- ll x = rhs.m;
- return b - s->b < (s->m - m) * x;
- }
- };
- struct HullDynamic : public multiset<Line> {
- bool bad(iterator y) {
- auto z = next(y);
- if (y == begin()) {
- if (z == end()) return 0;
- return y->m == z->m && y->b <= z->b;
- }
- auto x = prev(y);
- if (z == end()) return y->m == x->m && y->b <= x->b;
- return (x->b - y->b) * (z->m - y->m) >= (y->b - z->b) * (y->m - x->m);
- }
- void insert_line(ll m, ll b) {
- auto y = insert({m, b});
- y->succ = [=] { return next(y) == end() ? 0 : &*next(y); };
- if (bad(y)) {
- erase(y);
- return;
- }
- while (next(y) != end() && bad(next(y))) erase(next(y));
- while (y != begin() && bad(prev(y))) erase(prev(y));
- }
- ll eval(ll x) {
- auto l = *lower_bound((Line) {x, is_query});
- return l.m * x + l.b;
- }
- };
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