Submission #529389

#TimeUsernameProblemLanguageResultExecution timeMemory
529389msg555Aliens (IOI16_aliens)C++14
0 / 100
1 ms292 KiB
#include "aliens.h" #include <vector> #include <algorithm> #include <iostream> #include <set> using namespace std; const long long INF = 0x3FFFFFFFFFFFFFFFLL; long long squared(int x) { return 1ll * x * x; } long long cross_x(pair<long long, long long> X, pair<long long, long long> Y) { /* Returns the first x >= to when the lines intersect */ long long db = X.first - Y.first; long long dc = Y.second - X.second; if (db == 0) { return db < 0 ? -INF : INF; } if (db < 0) { db = -db; dc = -dc; } if (dc < 0) { return dc / db; } return (dc + db - 1) / db; } struct dumb_hull { bool insert(long long a, long long b) { lns.push_back(make_pair(a, b)); return true; } long long get(long long x) const { long long res = -INF; for (auto ln : lns) { res = max(res, ln.first * x + ln.second); } return res; } vector<pair<long long, long long> > lns; }; struct line_hull { /* Implements a max hull, get the max ax+b for all inserted lines. */ bool insert(long long a, long long b) { /* Insert line ax+b */ // cout << "INSERT " << a << ", " << b << endl; auto ln = make_pair(a, b); auto it = st.lower_bound(ln); bool is_last = it == st.end(); if (!is_last && ln.first == it->first) { return false; } auto jt = it; bool is_first = it == st.begin(); if (!is_first) { --it; if (it->first == ln.first) { if (it == st.begin()) { is_first = true; } else { --it; } } } long long lft_x = is_first ? -INF : cross_x(*it, ln); long long rht_x = is_last ? INF : cross_x(ln, *jt); if (rht_x <= lft_x) { return false; } if (!is_first) { while (it != st.begin()) { auto kt = it--; long long prev_lft_x = cross_x(*it, *kt); if (prev_lft_x < lft_x) { ++it; break; } lft_x = cross_x(*it, ln); } ++it; } if (!is_last) { while (true) { auto kt = jt++; if (jt == st.end()) { break; } long long prev_rht_x = cross_x(*kt, *jt); if (rht_x < prev_rht_x) { break; } rht_x = prev_rht_x; } --jt; } crs.erase( crs.lower_bound(make_pair(lft_x + (is_first ? -1 : 0), make_pair(INF, INF))), crs.lower_bound(make_pair(rht_x, make_pair(INF, INF))) ); crs.insert(make_pair(lft_x, ln)); if (!is_last) { crs.insert(make_pair(rht_x, *jt)); } st.erase(it, jt); st.insert(ln); // cout << st.size() << ", " << crs.size() << endl; return true; } long long get(long long x) const { auto it = crs.lower_bound(make_pair(x, make_pair(-INF, -INF))); --it; return it->second.first * x + it->second.second; } set<pair<long long, long long> > st; set<pair<long long, pair<long long, long long> > > crs; }; long long take_photos(int N, int M, int K, vector<int> R, vector<int> C) { vector<pair<int, int> > A; for (int i = 0; i < N; i++) { int ri = R[i]; int ci = C[i]; if (ri > ci) swap(ri, ci); A.push_back(make_pair(ci, ci - ri)); } sort(A.begin(), A.end()); int j = 0; for (auto p : A) { while (j > 0 && p.second >= A[j - 1].second + p.first - A[j - 1].first) { --j; } A[j++] = p; } A.resize(j); N = j; vector<long long> ADJ(N + 1, 0); for (int i = 1; i < N; i++) { ADJ[i] = squared(max(0, 1 + A[i].second - A[i].first + A[i - 1].first)); } long long INF = squared(M + 1); vector<long long> DP(N + 1, INF); vector<long long> DP2(N + 1, INF); DP[0] = 0; for (int k = 0; k < K; k++) { line_hull hl; //dumb_hull hl; for (int i = 0; i <= N; i++) { if (i) { long long x = A[i - 1].first; DP[i] = -hl.get(x) + squared(x); } /* for (int j = 0; j < i; j++) { DP[i] = min( DP[i], DP[j] + squared(1 + A[j].second + A[i - 1].first - A[j].first) - ADJ[j] ); } */ // x^2 + bx + c where x = A[i - 1].first long long sadd = 1 + A[i].second - A[i].first; long long b = 2 * sadd; long long c = squared(sadd) + DP[i] - ADJ[i]; hl.insert(-b, -c); } DP.swap(DP2); } return DP[N]; }
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