Submission #1207389

#TimeUsernameProblemLanguageResultExecution timeMemory
1207389countlessRectangles (IOI19_rect)C++20
72 / 100
5094 ms1023484 KiB
#include "rect.h" #include <bits/stdc++.h> using namespace std; typedef long long ll; typedef long double ld; const ll MOD = 998244353; // const ll INF = 1e18; const int INF = 5e3; const ld EPS = 1e-12; #define endl "\n" #define sp <<" "<< #define REP(i, a, b) for(ll i = a; i < b; i++) #define dbg(x) cout << #x << " = " << x << endl #define mp make_pair #define pb push_back #define fi first #define se second #define fast_io() ios_base::sync_with_stdio(false); cin.tie(NULL) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() #define sz(x) ((ll)(x).size()) struct custom_hash { static uint64_t splitmix64(uint64_t x) { // http://xorshift.di.unimi.it/splitmix64.c x += 0x9e3779b97f4a7c15; x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9; x = (x ^ (x >> 27)) * 0x94d049bb133111eb; return x ^ (x >> 31); } size_t operator()(uint64_t x) const { static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count(); return splitmix64(x + FIXED_RANDOM); } }; struct pair_hash { size_t operator()(const pair<int, int> &p) const { size_t h1 = custom_hash{}(p.first); size_t h2 = custom_hash{}(p.second); return h1 ^ (h2 << 1); } }; struct rect_hash { size_t operator()(const pair<pair<int, int>, pair<int, int>> &p) const { size_t h1 = pair_hash{}(p.first); size_t h2 = pair_hash{}(p.second); return h1 ^ (h2 << 1); } }; using rect = pair<pair<int, int>, pair<int, int>>; template <typename Key, typename Value> using hash_map = unordered_map<Key, Value, custom_hash>; mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); // uniform_int_distribution<int>(a, b)(rng); // shuffle(all(a), rng); struct stuff { short coll, colr, rowl, rowr; stuff(short coll = -INF, short colr = INF, short rowl = -INF, short rowr = INF) : coll(coll), colr(colr), rowl(rowl), rowr(rowr) {;;} // use static for ref static stuff merge(const stuff &a, const stuff &b) { return stuff{min(a.coll, b.coll), max(a.colr, b.colr), min(a.rowl, b.rowl), max(a.rowr, b.rowr)}; } }; const stuff nothing = stuff{INF, -INF, INF, -INF}; struct twotree { int n, m; vector<vector<stuff>> tree; const vector<vector<stuff>> &base; // avoid copies twotree(const vector<vector<stuff>> &base) : n(base.size()), m(base[0].size()), tree(4*n, vector<stuff>(4*m)), base(base) { buildX(1, 0, n-1); } void buildY(int x, int l, int r, int y, int ll, int rr) { if (ll == rr) { if (l == r) { tree[x][y] = base[l][ll]; } else { tree[x][y] = stuff::merge(tree[x*2][y], tree[x*2+1][y]); } } else { int m = (ll+rr)/2; buildY(x, l, r, y*2, ll, m); buildY(x, l, r, y*2+1, m+1, rr); tree[x][y] = stuff::merge(tree[x][y*2], tree[x][y*2+1]); } } void buildX(int x, int l, int r) { if (l != r) { int m = (l+r)/2; buildX(x*2, l, m); buildX(x*2+1, m+1, r); } buildY(x, l, r, 1, 0, m-1); } stuff queryY(int x, int y, int ll, int rr, int qll, int qrr) { if (qrr < ll or qll > rr) { return nothing; } if (qll <= ll and rr <= qrr) { return tree[x][y]; } int m = (ll+rr)/2; return stuff::merge(queryY(x, y*2, ll, m, qll, qrr), queryY(x, y*2+1, m+1, rr, qll, qrr)); } stuff queryX(int x, int l, int r, int ql, int qr, int qll, int qrr) { if (qr < l or ql > r) { return nothing; } if (ql <= l and r <= qr) { return queryY(x, 1, 0, m-1, qll, qrr); } int m = (l+r)/2; return stuff::merge(queryX(x*2, l, m, ql, qr, qll, qrr), queryX(x*2+1, m+1, r, ql, qr, qll, qrr)); } stuff query(int x, int y, int xx, int yy) { return queryX(1, 0, n-1, x, xx, y, yy); } }; ll count_rectangles(vector<vector<int>> a) { short n = a.size(), m = a[0].size(); vector<vector<stuff>> base(n, vector<stuff>(m)); ll ans = 0; stack<short> st; // O(nm) for (short i = 0; i < n; i++) { while (!st.empty()) st.pop(); for (short j = 0; j < m; j++) { while (!st.empty() and a[i][st.top()] <= a[i][j]) { st.pop(); } if (!st.empty()) { base[i][j].rowl = st.top(); } st.push(j); } while (!st.empty()) st.pop(); for (short j = m-1; j >= 0; j--) { while (!st.empty() and a[i][st.top()] <= a[i][j]) { st.pop(); } if (!st.empty()) { base[i][j].rowr = st.top(); } st.push(j); } } for (short i = 0; i < m ; i++) { while (!st.empty()) st.pop(); for (short j = 0; j < n; j++) { while (!st.empty() and a[st.top()][i] <= a[j][i]) { st.pop(); } if (!st.empty()) { base[j][i].coll = st.top(); } st.push(j); } while (!st.empty()) st.pop(); for (short j = n-1; j >= 0; j--) { while (!st.empty() and a[st.top()][i] <= a[j][i]) { st.pop(); } if (!st.empty()) { base[j][i].colr = st.top(); } st.push(j); } } twotree tree(base); auto in = [&](short x, short y) -> bool { return (0 < x and x < n-1 and 0 < y and y < m-1); }; // O(1) unordered_map<rect, bool, rect_hash> vis; auto checkRect = [&](short x, short y, short xx, short yy) -> int { if (!in(x,y) or !in(xx, yy)) return 0; if (x > xx) swap(x, xx); if (y > yy) swap(y, yy); if (vis[{{x, y}, {xx, yy}}]) return 0; vis[{{x, y}, {xx, yy}}] = true; stuff q = tree.query(x, y, xx, yy); if (q.coll < x-1 or q.colr > xx+1 or q.rowl < y-1 or q.rowr > yy+1) { return 0; } return 1; }; // O(nm) for (short i = 1; i < n - 1; i++) { for (short j = 1; j < m - 1; j++) { stuff q = base[i][j]; if (q.coll == -INF or q.colr == INF or q.rowl == -INF or q.rowr == INF) { continue; } ans += checkRect(q.coll+1, q.rowl+1, q.colr-1, q.rowr-1); } } return ans; } // int main() { // int n, m; cin >> n >> m; // vector<vector<int>> a(n, vector<int>(m)); // REP(i, 0, n) { // REP(j, 0, m) { // cin >> a[i][j]; // } // } // cout << count_rectangles(a) << endl; // }
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