Submission #1073646

#TimeUsernameProblemLanguageResultExecution timeMemory
1073646fv3Radio Towers (IOI22_towers)C++17
23 / 100
544 ms6600 KiB
#include "towers.h" #include <bits/stdc++.h> using namespace std; const int INF = 1 << 30; int N; vector<int> H; struct node { int mn; int index; }; node merge(const node a, const node b) { return a.mn < b.mn ? a : b; } const node empty_node = {INF, 0}; int nt; vector<int> st_mx; vector<node> st_mn; node get_min_range(int l, int r, int k, int tl, int tr) { if (tr < l || tl > r) return empty_node; if (tl >= l && tr <= r) return st_mn[k]; int c = (tl + tr) / 2; return merge(get_min_range(l, r, k*2, tl, c), get_min_range(l, r, k*2|1, c+1, tr)); } void set_min(int i) { i += nt; st_mn[i] = empty_node; for (i /= 2; i >= 1; i /= 2) st_mn[i] = merge(st_mn[i*2], st_mn[i*2|1]); } int get_max_range(int l, int r, int k, int tl, int tr) { if (tr < l || tl > r) return 0; if (tl >= l && tr <= r) return st_mx[k]; int c = (tl + tr) / 2; return max(get_max_range(l, r, k*2, tl, c), get_max_range(l, r, k*2|1, c+1, tr)); } void init(int N_, vector<int> H_) { N = N_; H = H_; nt = 1; while (nt < N) nt <<= 1; st_mx = vector<int>(nt*2); st_mn = vector<node>(nt*2, empty_node); for (int i = 0; i < N; i++) { st_mx[nt + i] = H[i]; st_mn[nt + i] = {H[i], i}; } for (int i = nt - 1; i >= 1; i--) { st_mx[i] = max(st_mx[i*2], st_mx[i*2|1]); st_mn[i] = merge(st_mn[i*2], st_mn[i*2|1]); } } int max_towers(int L, int R, int D) { // You should always lease the smallest tower // No two adjacent towers can be leased int res = 0; set<int> leased; while (true) { node cnd = get_min_range(L, R, 1, 0, nt - 1); if (cnd.mn == INF) break; if (!leased.size()) { res++; leased.insert(cnd.index); for (int i = max(L, cnd.index-1); i <= min(R, cnd.index + 1); i++) set_min(i); continue; } if (*leased.begin() < cnd.index) { int l = *--leased.lower_bound(cnd.index); int mx = get_max_range(l, cnd.index, 1, 0, nt - 1); if (mx - cnd.mn < D) { set_min(cnd.index); continue; } } if (*--leased.end() > cnd.index) { int r = *leased.lower_bound(cnd.index); int mx = get_max_range(cnd.index, r, 1, 0, nt - 1); if (mx - cnd.mn < D) { set_min(cnd.index); continue; } } res++; leased.insert(cnd.index); for (int i = max(L, cnd.index-1); i <= min(R, cnd.index + 1); i++) set_min(i); } return res; }
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