#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int maxn = 1e5+5;
typedef long double ld;
const ll INF = 1LL<<62;
struct FN
{
ll m, b; //in this case, function is a line
bool is_query;
FN(ll _m, ll _b, bool is = false) : m(_m), b(_b), is_query(is) {}
mutable function<ld()> xRight; //right intersection point of line in hull, is infinity for rightmost line
ll eval(ll x) const {
return m*x + b;
}
ld intersect(const FN& r) const { //returns x coordinate of intersection
//assert(m != r.m);
return (ld)(r.b-b)/(ld)(m-r.m);
}
friend bool comp(const FN& l1, const FN& l2, const FN& l) {
//order in deque: l1, l2, l
//true --> l2 is unnecessary
ld x1 = l1.intersect(l);
ld x2 = l1.intersect(l2);
return x1 <= x2;
}
bool operator<(const FN& rhs) const {
//make sure to check which </> should be used
if (!rhs.is_query) return m > rhs.m;
//greater since we want smaller slopes to the right
ll x = rhs.m;
return xRight() < (ld)x; //always stays the same
}
};
//goal: dynamic variant of convex hull
//insert, delete, and query in O(log n)
struct Hull: public set<FN> //convex hull for maximum
{
void addFN(FN fn) {
Hull::iterator it = lower_bound(fn);
if (it != end() && it->m == fn.m) {
if (it->b >= fn.b) return; //no need to consider it
//this line must be changed based on +/- slope!!!
erase(it);
}
it = insert(fn).first;
//check if what we just inserted is necessary
if (it != begin() && next(it) != end()) {
if (comp(*prev(it),*it,*next(it))) {
//not needed
erase(it);
return;
}
}
it->xRight = [=] { return next(it) == end() ? INF : it->intersect(*next(it)); };
//function pointer magic
//Removes unnecessary lines above and below
Hull::iterator b1, b2, f1, f2;
while (true) {
if (it == begin()) break;
else {
b1 = prev(it);
if (b1 == begin()) break;
else {
b2 = prev(b1);
if (comp(*b2,*b1,*it)) {
erase(b1);
}
else break;
}
}
}
while (true) {
f1 = next(it);
if (f1 == end()) break;
else {
f2 = next(f1);
if (f2 == end()) break;
else {
if (comp(*it,*f1,*f2)) {
erase(f1);
}
else break;
}
}
}
}
ll query(ll x) {
//if (this->empty()) return 0; //because querying for maximum
assert(!this->empty());
auto it = lower_bound(FN(x,0,true));
return it->eval(x);
}
};
//dp[i] = min_{1 <= j < i} (h[i]-h[j])^2 + sum(w[j+1]..w[i-1]) + dp[j]
// = (h[i]-h[j])^2 + pfx[i-1]-pfx[j]+dp[j]
// = h[i]^2 - 2h[i]*h[j] + h[j]^2 + pfx[i-1] - pfx[j] + dp[j]
// = (h[i]^2+pfx[i-1]) + (-2h[j])*h[i] + (dp[j]-pfx[j]) + h[j]^2
// = (independent) + (mx) - b
// So each j has (m,b) = (-2h[j],dp[j]-pfx[j]+h[j]^2)
// Unfortunately, the h[i]'s and h[j]'s aren't monotonic, so we have implement a hull w/ dynamic
// queries/insertions
//
int n;
ll h[maxn], w[maxn], pfx[maxn];
ll dp[maxn];
int main()
{
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> h[i];
}
for (int i = 1; i <= n; i++) {
cin >> w[i];
pfx[i] = w[i] + pfx[i-1];
}
Hull hull;
hull.addFN(FN(-2*h[1],-pfx[1]+h[1]*h[1]));
for (int i = 2; i <= n; i++) {
ll q = hull.query(h[i]) + (h[i]*h[i])+pfx[i-1];
/*
cout << hull.query(h[i]) << '\n';
cout << i << ": " << q << '\n';
*/
hull.addFN(FN(-2*h[i],q-pfx[i]+h[i]*h[i]));
if (i == n) {
cout << q << '\n';
}
}
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
384 KB |
Output is correct |
| 2 |
Correct |
3 ms |
384 KB |
Output is correct |
| 3 |
Incorrect |
2 ms |
384 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
83 ms |
3832 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
384 KB |
Output is correct |
| 2 |
Correct |
3 ms |
384 KB |
Output is correct |
| 3 |
Incorrect |
2 ms |
384 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
