#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define LL long long
#define FOR(i,a,b) for (int i = (a); i <= (b); i++)
#define FORD(i,a,b) for (int i = (a); i >= (b); i--)
#define REP(i,n) FOR(i,0,(int)(n)-1)
#define st first
#define nd second
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define VI vector<int>
#define PII pair<int,int>
#define LD long double
template<class C> void mini(C& a4, C b4) { a4 = min(a4, b4); }
template<class C> void maxi(C& a4, C b4) { a4 = max(a4, b4); }
template<class T> ostream &operator<<(ostream &os, vector<T> V){
os<<"[";for(auto vv:V)os<<vv<<",";return os<<"]";
}
template<class L, class R> ostream &operator<<(ostream &os, pair<L,R> P) {
return os << "(" << P.st << "," << P.nd << ")";
}
template<class TH> void _dbg(const char *sdbg, TH h){cerr<<sdbg<<"="<<h<<"\n";}
template<class TH, class... TA> void _dbg(const char *sdbg, TH h, TA... a) {
while(*sdbg!=',')cerr<<*sdbg++;
cerr<<"="<<h<<","; _dbg(sdbg+1, a...);
}
#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (__VA_ARGS__)
#define cerr if(0)cout
#endif
vector<VI> computePrimeDivisors(int n) {
vector<VI> divisors(n + 1);
FOR(i, 2, n) {
if (divisors[i].empty()) {
for (int j = i; j <= n; j += i) {
divisors[j].PB(i);
}
}
}
return divisors;
}
optional<int> get_prev(set<int>& s, int x) {
auto it = s.find(x);
if (it == s.begin()) return nullopt;
return *prev(it);
}
optional<int> get_prev_2(set<int>& s, int x) {
auto p = get_prev(s, x);
if (!p) return nullopt;
return get_prev(s, *p);
}
optional<int> get_next(set<int>& s, int x) {
auto it = s.find(x);
auto nxt = next(it);
if (nxt == s.end()) return nullopt;
return *nxt;
}
optional<int> get_next_2(set<int>& s, int x) {
auto n = get_next(s, x);
if (!n) return nullopt;
return get_next(s, *n);
}
// [prev_2, prev, next, next_2]
array<optional<int>, 4> get_neighbours(set<int>& s, int x) {
array<optional<int>, 4> res = {nullopt, nullopt, nullopt, nullopt};
auto it = s.find(x);
if (it != s.begin()) {
auto p = prev(it);
res[1] = *p;
if (p != s.begin()) res[0] = *prev(p);
}
auto nxt = next(it);
if (nxt != s.end()) {
res[2] = *nxt;
auto nxt2 = next(nxt);
if (nxt2 != s.end()) res[3] = *nxt2;
}
return res;
}
struct MaxSegTree {
int n;
vector<PII> tree; // {value, -index} so max gives smallest index on tie
MaxSegTree() : n(0) {}
MaxSegTree(int n) : n(n), tree(2 * n, {0, 0}) {
REP(i, n) tree[n + i] = {0, -i};
}
void update(int i, int delta) {
int pos = n + i;
tree[pos].st += delta;
for (pos >>= 1; pos >= 1; pos >>= 1)
tree[pos] = max(tree[2 * pos], tree[2 * pos + 1]);
}
// returns {max_value, index}
PII query() {
auto [val, neg_idx] = tree[1];
return {val, -neg_idx};
}
};
const int K = 10; // number of interesting primes to track
int cnt_replay = 0, cnt_recalc = 0, cnt_recalc_interesting = 0;
long long total_dist_scan = 0, total_replay_len = 0, total_prime_mod_alloc = 0;
struct Tracking {
set<int> stones;
unordered_map<int, int> distances; // prime p -> count of distances divisible by p
vector<VI> prime_divisors; // prime_divisors[x] = list of prime factors of x
unordered_map<int, unordered_map<int,int>> prime_mod; // prime_mod[p][r] = # stones with stone % p == r
unordered_map<int, int> prime_freshness; // prime_freshness[p] = time t at which prime_mod[p] was last computed
VI interesting; // up to K interesting prime divisors
VI q; // queries
int t; // current query index (0-based)
int n; // max stone value
};
int get_n(Tracking & t){
return SZ(t.stones);
}
void add_distance(Tracking & t, int dist) {
debug("add", dist);
for (int p : t.prime_divisors[dist]) {
t.distances[p]++;
}
}
void remove_distance(Tracking & t, int dist) {
debug("rem", dist);
for (int p : t.prime_divisors[dist]) {
t.distances[p]--;
if (t.distances[p] < 0) debug("NEGATIVE", p, t.distances[p], dist);
if (t.distances[p] == 0) t.distances.erase(p);
}
}
void refresh_prime(Tracking & t, int p) {
int replay_cost = t.t - t.prime_freshness[p];
int recalc_cost = SZ(t.stones);
if (replay_cost <= recalc_cost) {
cnt_replay++;
total_replay_len += t.t - t.prime_freshness[p];
FOR(i, t.prime_freshness[p], t.t - 1) {
int pos = abs(t.q[i]);
int sign = (t.q[i] > 0) ? 1 : -1;
t.prime_mod[p][pos % p] += sign;
}
} else {
cnt_recalc++;
t.prime_mod[p].clear();
for (int s : t.stones) {
t.prime_mod[p][s % p]++;
}
}
t.prime_freshness[p] = t.t;
}
bool is_interesting(Tracking & t, int p) {
auto it = t.distances.find(p);
if (it == t.distances.end()) return false;
return it->second >= get_n(t) / 4;
}
void recalc_interesting(Tracking & t) {
cnt_recalc_interesting++;
total_dist_scan += SZ(t.distances);
int lb = (get_n(t) + 1) / 2; // ceil(stones/2), lower bound from p=2
vector<PII> candidates; // {count, prime}
for (auto& [p, cnt] : t.distances) {
if (p > 2 && (t.n / p) < lb) continue; // can't beat p=2 lower bound
if (cnt >= get_n(t) / 4) {
candidates.PB({cnt, p});
}
}
sort(ALL(candidates), greater<PII>());
t.interesting.clear();
t.interesting.PB(2);
REP(i, min((int)K, SZ(candidates))) {
if (candidates[i].nd != 2)
t.interesting.PB(candidates[i].nd);
}
for (int p : t.interesting) {
refresh_prime(t, p);
}
}
void insert_stone(int x, Tracking & t) {
t.stones.insert(x);
auto nb = get_neighbours(t.stones, x);
REP(i, 4) if (nb[i]) add_distance(t, abs(x - *nb[i]));
if (nb[0] && nb[2]) remove_distance(t, *nb[2] - *nb[0]); // prev_2-next was next-nb, gone
if (nb[1] && nb[3]) remove_distance(t, *nb[3] - *nb[1]); // prev-next_2 was next-nb, gone
for (int p : t.interesting) {
refresh_prime(t, p);
}
recalc_interesting(t);
}
void remove_stone(int x, Tracking & t) {
auto nb = get_neighbours(t.stones, x);
REP(i, 4) if (nb[i]) remove_distance(t, abs(x - *nb[i]));
if (nb[0] && nb[2]) add_distance(t, *nb[2] - *nb[0]); // prev_2-next becomes next-nb
if (nb[1] && nb[3]) add_distance(t, *nb[3] - *nb[1]); // prev-next_2 becomes next-nb
for (int p : t.interesting) {
refresh_prime(t, p);
}
t.stones.erase(x);
recalc_interesting(t);
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, Q;
cin >> n >> Q;
Tracking t;
t.n = n;
t.q = VI(Q);
t.t = 0;
t.prime_divisors = computePrimeDivisors(n);
REP(i, Q) {
cin >> t.q[i];
}
REP(i, Q) {
t.t++;
int pos = abs(t.q[i]);
if (t.stones.count(pos)) {
t.q[i] = -pos; // negative = remove
remove_stone(pos, t);
} else {
t.q[i] = pos; // positive = insert
insert_stone(pos, t);
}
int ans = min((int)1, get_n(t));
for (int p : t.interesting) {
for (auto& [r, cnt] : t.prime_mod[p]) {
maxi(ans, cnt);
}
}
debug(i, pos, ans, t.interesting, get_n(t));
VI dist_keys, dist_vals;
for (auto& [p, cnt] : t.distances) { dist_keys.PB(p); dist_vals.PB(cnt); }
debug(dist_keys, dist_vals);
// if (i % 10000 == 0) {
// cerr << "i=" << i << " replay=" << cnt_replay << " recalc=" << cnt_recalc
// << " recalc_interesting=" << cnt_recalc_interesting
// << " total_dist_scan=" << total_dist_scan
// << " total_replay_len=" << total_replay_len
// << " dist_size=" << SZ(t.distances)
// << " stones=" << get_n(t) << endl;
// }
cout << ans << "\n";
}
// cerr << "replay=" << cnt_replay << " recalc=" << cnt_recalc
// << " recalc_interesting=" << cnt_recalc_interesting
// << " total_dist_scan=" << total_dist_scan
// << " total_replay_len=" << total_replay_len << endl;
return 0;
}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 | #include <bits/stdc++.h> using namespace std; #define PB push_back #define LL long long #define FOR(i,a,b) for (int i = (a); i <= (b); i++) #define FORD(i,a,b) for (int i = (a); i >= (b); i--) #define REP(i,n) FOR(i,0,(int)(n)-1) #define st first #define nd second #define ALL(x) (x).begin(), (x).end() #define SZ(x) ((int)(x).size()) #define VI vector<int> #define PII pair<int,int> #define LD long double template<class C> void mini(C& a4, C b4) { a4 = min(a4, b4); } template<class C> void maxi(C& a4, C b4) { a4 = max(a4, b4); } template<class T> ostream &operator<<(ostream &os, vector<T> V){ os<<"[";for(auto vv:V)os<<vv<<",";return os<<"]"; } template<class L, class R> ostream &operator<<(ostream &os, pair<L,R> P) { return os << "(" << P.st << "," << P.nd << ")"; } template<class TH> void _dbg(const char *sdbg, TH h){cerr<<sdbg<<"="<<h<<"\n";} template<class TH, class... TA> void _dbg(const char *sdbg, TH h, TA... a) { while(*sdbg!=',')cerr<<*sdbg++; cerr<<"="<<h<<","; _dbg(sdbg+1, a...); } #ifdef LOCAL #define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__) #else #define debug(...) (__VA_ARGS__) #define cerr if(0)cout #endif vector<VI> computePrimeDivisors(int n) { vector<VI> divisors(n + 1); FOR(i, 2, n) { if (divisors[i].empty()) { for (int j = i; j <= n; j += i) { divisors[j].PB(i); } } } return divisors; } optional<int> get_prev(set<int>& s, int x) { auto it = s.find(x); if (it == s.begin()) return nullopt; return *prev(it); } optional<int> get_prev_2(set<int>& s, int x) { auto p = get_prev(s, x); if (!p) return nullopt; return get_prev(s, *p); } optional<int> get_next(set<int>& s, int x) { auto it = s.find(x); auto nxt = next(it); if (nxt == s.end()) return nullopt; return *nxt; } optional<int> get_next_2(set<int>& s, int x) { auto n = get_next(s, x); if (!n) return nullopt; return get_next(s, *n); } // [prev_2, prev, next, next_2] array<optional<int>, 4> get_neighbours(set<int>& s, int x) { array<optional<int>, 4> res = {nullopt, nullopt, nullopt, nullopt}; auto it = s.find(x); if (it != s.begin()) { auto p = prev(it); res[1] = *p; if (p != s.begin()) res[0] = *prev(p); } auto nxt = next(it); if (nxt != s.end()) { res[2] = *nxt; auto nxt2 = next(nxt); if (nxt2 != s.end()) res[3] = *nxt2; } return res; } struct MaxSegTree { int n; vector<PII> tree; // {value, -index} so max gives smallest index on tie MaxSegTree() : n(0) {} MaxSegTree(int n) : n(n), tree(2 * n, {0, 0}) { REP(i, n) tree[n + i] = {0, -i}; } void update(int i, int delta) { int pos = n + i; tree[pos].st += delta; for (pos >>= 1; pos >= 1; pos >>= 1) tree[pos] = max(tree[2 * pos], tree[2 * pos + 1]); } // returns {max_value, index} PII query() { auto [val, neg_idx] = tree[1]; return {val, -neg_idx}; } }; const int K = 10; // number of interesting primes to track int cnt_replay = 0, cnt_recalc = 0, cnt_recalc_interesting = 0; long long total_dist_scan = 0, total_replay_len = 0, total_prime_mod_alloc = 0; struct Tracking { set<int> stones; unordered_map<int, int> distances; // prime p -> count of distances divisible by p vector<VI> prime_divisors; // prime_divisors[x] = list of prime factors of x unordered_map<int, unordered_map<int,int>> prime_mod; // prime_mod[p][r] = # stones with stone % p == r unordered_map<int, int> prime_freshness; // prime_freshness[p] = time t at which prime_mod[p] was last computed VI interesting; // up to K interesting prime divisors VI q; // queries int t; // current query index (0-based) int n; // max stone value }; int get_n(Tracking & t){ return SZ(t.stones); } void add_distance(Tracking & t, int dist) { debug("add", dist); for (int p : t.prime_divisors[dist]) { t.distances[p]++; } } void remove_distance(Tracking & t, int dist) { debug("rem", dist); for (int p : t.prime_divisors[dist]) { t.distances[p]--; if (t.distances[p] < 0) debug("NEGATIVE", p, t.distances[p], dist); if (t.distances[p] == 0) t.distances.erase(p); } } void refresh_prime(Tracking & t, int p) { int replay_cost = t.t - t.prime_freshness[p]; int recalc_cost = SZ(t.stones); if (replay_cost <= recalc_cost) { cnt_replay++; total_replay_len += t.t - t.prime_freshness[p]; FOR(i, t.prime_freshness[p], t.t - 1) { int pos = abs(t.q[i]); int sign = (t.q[i] > 0) ? 1 : -1; t.prime_mod[p][pos % p] += sign; } } else { cnt_recalc++; t.prime_mod[p].clear(); for (int s : t.stones) { t.prime_mod[p][s % p]++; } } t.prime_freshness[p] = t.t; } bool is_interesting(Tracking & t, int p) { auto it = t.distances.find(p); if (it == t.distances.end()) return false; return it->second >= get_n(t) / 4; } void recalc_interesting(Tracking & t) { cnt_recalc_interesting++; total_dist_scan += SZ(t.distances); int lb = (get_n(t) + 1) / 2; // ceil(stones/2), lower bound from p=2 vector<PII> candidates; // {count, prime} for (auto& [p, cnt] : t.distances) { if (p > 2 && (t.n / p) < lb) continue; // can't beat p=2 lower bound if (cnt >= get_n(t) / 4) { candidates.PB({cnt, p}); } } sort(ALL(candidates), greater<PII>()); t.interesting.clear(); t.interesting.PB(2); REP(i, min((int)K, SZ(candidates))) { if (candidates[i].nd != 2) t.interesting.PB(candidates[i].nd); } for (int p : t.interesting) { refresh_prime(t, p); } } void insert_stone(int x, Tracking & t) { t.stones.insert(x); auto nb = get_neighbours(t.stones, x); REP(i, 4) if (nb[i]) add_distance(t, abs(x - *nb[i])); if (nb[0] && nb[2]) remove_distance(t, *nb[2] - *nb[0]); // prev_2-next was next-nb, gone if (nb[1] && nb[3]) remove_distance(t, *nb[3] - *nb[1]); // prev-next_2 was next-nb, gone for (int p : t.interesting) { refresh_prime(t, p); } recalc_interesting(t); } void remove_stone(int x, Tracking & t) { auto nb = get_neighbours(t.stones, x); REP(i, 4) if (nb[i]) remove_distance(t, abs(x - *nb[i])); if (nb[0] && nb[2]) add_distance(t, *nb[2] - *nb[0]); // prev_2-next becomes next-nb if (nb[1] && nb[3]) add_distance(t, *nb[3] - *nb[1]); // prev-next_2 becomes next-nb for (int p : t.interesting) { refresh_prime(t, p); } t.stones.erase(x); recalc_interesting(t); } int32_t main() { ios_base::sync_with_stdio(0); cin.tie(0); int n, Q; cin >> n >> Q; Tracking t; t.n = n; t.q = VI(Q); t.t = 0; t.prime_divisors = computePrimeDivisors(n); REP(i, Q) { cin >> t.q[i]; } REP(i, Q) { t.t++; int pos = abs(t.q[i]); if (t.stones.count(pos)) { t.q[i] = -pos; // negative = remove remove_stone(pos, t); } else { t.q[i] = pos; // positive = insert insert_stone(pos, t); } int ans = min((int)1, get_n(t)); for (int p : t.interesting) { for (auto& [r, cnt] : t.prime_mod[p]) { maxi(ans, cnt); } } debug(i, pos, ans, t.interesting, get_n(t)); VI dist_keys, dist_vals; for (auto& [p, cnt] : t.distances) { dist_keys.PB(p); dist_vals.PB(cnt); } debug(dist_keys, dist_vals); // if (i % 10000 == 0) { // cerr << "i=" << i << " replay=" << cnt_replay << " recalc=" << cnt_recalc // << " recalc_interesting=" << cnt_recalc_interesting // << " total_dist_scan=" << total_dist_scan // << " total_replay_len=" << total_replay_len // << " dist_size=" << SZ(t.distances) // << " stones=" << get_n(t) << endl; // } cout << ans << "\n"; } // cerr << "replay=" << cnt_replay << " recalc=" << cnt_recalc // << " recalc_interesting=" << cnt_recalc_interesting // << " total_dist_scan=" << total_dist_scan // << " total_replay_len=" << total_replay_len << endl; return 0; } |
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