Submission #1192004

#	Time	Username	Problem	Language	Result	Execution time	Memory
1192004		shirokito	Building Bridges (CEOI17_building)	C++20	100 / 100	39 ms	9796 KiB

building

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define el '\n'

const int N = 1e6 + 24; 
const ll INF = 4e18;

int n; ll h[N], w[N];
ll pre[N], dp[N];

struct Line {
    mutable ll k, m, p;
    bool operator < (const Line& o) const { return k < o.k; }
    bool operator < (ll x) const { return p < x; }
};
 
struct CHT : multiset<Line, less<>> {
    static const ll inf = LLONG_MAX;
    ll div(ll a, ll b) {
        return a / b - ((a ^ b) < 0 && a % b); 
    }
    bool isect(iterator x, iterator y) {
        if (y == end()) return x->p = inf, 0;
        if (x->k == y->k) x->p = x->m > y->m ? inf : -inf;
        else x->p = div(y->m - x->m, x->k - y->k);
        return x->p >= y->p;
    }
    void add(ll k, ll m) {
        auto z = insert({k, m, 0}), y = z++, x = y;
        while (isect(y, z)) z = erase(z);
        if (x != begin() && isect(--x, y)) isect(x, y = erase(y));
        while ((y = x) != begin() && (--x)->p >= y->p)
        isect(x, erase(y));
    }
    ll get(ll x) {
        assert(!empty());
        auto l = *lower_bound(x);
        return l.k * x + l.m;
    }
} cht;

// struct Line {
//     ll a, b;
//     ll calc(ll x) { return a * x + b; }
// };

// struct Lichao {
//     int n; vector<Line> t;

//     Lichao(int sz) : t(4 * sz + 24, {0, LLONG_MAX}), n(sz) {}

//     void update(int id, int l, int r, Line f) {
//         if (l == r) {
//             if (f.calc(l) < t[id].calc(l)) t[id] = f;
//             return;
//         }

//         int mid = (l + r) >> 1;
//         if (f.calc(mid) < t[id].calc(mid)) swap(f, t[id]);

//         if (f.calc(l) < t[id].calc(l)) update(2 * id, l, mid, f);
//         else update(2 * id + 1, mid + 1, r, f);
//     }

//     ll get(int id, int l, int r, int i) {
//         int mid = (l + r) >> 1;
//         ll cur = t[id].calc(l);

//         if (i == mid) return cur;
//         else if (i < mid) return min(get(2 * id, l, mid, i), cur);
//         else return min(get(2 * id + 1, mid + 1, r, i), cur);
//     }
// };

void solve() {
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> h[i];
    for (int i = 1; i <= n; i++) cin >> w[i];

    for (int i = 1; i <= n; i++) {
        pre[i] = pre[i - 1] + w[i];
    }

    dp[1] = 0;
    for (int i = 1; i <= n; i++) {
        if (i > 1) dp[i] = h[i] * h[i] + pre[i - 1] - cht.get(h[i]);
        cht.add(2 * h[i], -(dp[i] + h[i] * h[i] - pre[i]));

        // dp[i] = INF;
        // for (int j = 1; j < i; j++) {
        //     dp[i] = min(dp[i], h[i] * h[i] + pre[i - 1] - 2 * h[i] * h[j] + dp[j] + h[j] * h[j] - pre[j]);
        // }
    }

    cout << dp[n] << el;
}

int main() {
    cin.tie(NULL) -> sync_with_stdio(false);

    #define task "file"
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }

    int T = 1; // cin >> T;
    while (T--) solve();
}

Compilation message (stderr)

building.cpp: In function 'int main()':
building.cpp:104:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  104 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
building.cpp:105:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  105 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40