Submission #1074296

#TimeUsernameProblemLanguageResultExecution timeMemory
1074296Gromp15Radio Towers (IOI22_towers)C++17
14 / 100
4085 ms2392 KiB
#include <bits/stdc++.h> #include "towers.h" #define ll long long #define ar array #define sz(x) (int)x.size() #define all(x) x.begin(), x.end() using namespace std; template<typename T> bool ckmin(T &a, const T &b ) { return a > b ? a = b, 1 : 0; } template<typename T> bool ckmax(T &a, const T &b ) { return a < b ? a = b, 1 : 0; } int n; vector<int> h, h2, pref; int D; int test(int i) { return (i && i+1 < n && ((h[i] > h[i-1] && h[i] > h[i+1]))); } bool one_peak = 1; int peak = -1; void init(int N, std::vector<int> H) { n = N; h = H; h2 = H; sort(all(h2)); h2.erase(unique(all(h2)), h2.end()); for (int &x : h) x = lower_bound(all(h2), x) - h2.begin(); pref.resize(n); for (int i = 0; i < n; i++) { pref[i] = test(i) + (i ? pref[i-1] : 0); } peak = max_element(all(h)) - h.begin(); for (int i = peak-1; i >= 0; i--) one_peak &= h[i] < h[i+1]; for (int i = peak+1; i < n; i++) one_peak &= h[i] < h[i-1]; } struct seg { int N; vector<int> tree; seg(int n) : N(1<<(__lg(n)+1)), tree(2*N, -1e9) {} void update(int pos, int x) { for (int i = pos + N; i; i >>= 1) ckmax(tree[i], x); } int query(int node, int nl, int nr, int ql, int qr) { if (ql > nr || qr < nl) return -1e9; if (ql <= nl && nr <= qr) return tree[node]; int mid = (nl+nr)/2; return max(query(node*2, nl, mid, ql, qr), query(node*2+1, mid+1, nr, ql, qr)); } int query(int l, int r) { return query(1, 0, N-1, l, r); } }; int Q = 0; int max_towers(int L, int R, int _D) { D = _D; if (one_peak) { return 1 + (L < peak && R > peak && (max(h[L], h[R]) <= h[peak] - D)); } if (Q++ == -1) { const int N = sz(h2); seg st0(N), st1(N); for (int i = L; i <= R; i++) { auto it = lower_bound(all(h2), h2[h[i]] + D); if (it != h2.end()) { st1.update(h[i], st0.query(it - h2.begin(), N - 1) + 1); } auto it2 = upper_bound(all(h2), h2[h[i]] - D); if (it2 != h2.begin()) { it2--; st0.update(h[i], st1.query(0, it2 - h2.begin())); } st1.update(h[i], 1); } return st1.query(0, N-1); } if (D == 1) { return pref[R] - (L ? pref[L-1] : 0) + 1 - test(L) - test(R) + (L == R ? test(L) : 0); } int ans = 1; set<int> SL, SR; for (int i = L+1; i <= R-1; i++) if (h[i] > h[i-1] && h[i] > h[i+1]) { int l = -1, r = -1; for (int j = i-1; j >= L; j--) { if (h2[h[i]] - D >= h2[h[j]]) { if (SL.count(j)) break; l = j; } } for (int j = i+1; j <= R; j++) { if (h2[h[i]] - D >= h2[h[j]]) { if (SR.count(j)) break; r = j; } } if (~l && ~r) { ans++; SL.insert(l); SR.insert(r); } } return ans; }
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