#include "sequence.h"
#include <bits/stdc++.h>
#define SZ(s) ((int) ((s).size()))
using namespace std;
vector<int> medians(const vector<int> values) {
int n = SZ(values);
assert(n > 0);
if (n % 2 == 0) {
return {values[n/2 - 1], values[n / 2]};
} else {
return {values[n/2]};
}
}
int sub1(const vector<int>& a) {
int n = SZ(a);
int res = 0;
for (int l = 0; l < n; ++l) {
for (int r = l; r < n; ++r) {
vector<int> b(a.begin() + l, a.begin() + r + 1);
unordered_map<int, int> cnt;
for (int val : b) cnt[val] += 1;
sort(b.begin(), b.end());
auto meds = medians(b);
for (int med : meds) {
res = max(res, cnt[med]);
}
}
}
return res;
}
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
using namespace __gnu_pbds;
int sub2(const vector<int>& a) {
int n = SZ(a);
int res = 0;
for (int l = 0; l < n; ++l) {
unordered_map<int, int> cnt;
ordered_set values;
for (int r = l; r < n; ++r) {
cnt[a[r]]++;
values.insert(a[r]);
int k = SZ(values);
if (k % 2 == 0) {
res = max(res, cnt[*values.find_by_order(k / 2 - 1)]);
res = max(res, cnt[*values.find_by_order(k / 2)]);
} else {
res = max(res, cnt[*values.find_by_order(k / 2)]);
}
}
}
return res;
}
bool is_sub_3(const std::vector<int> a) {
auto mit = max_element(a.begin(), a.end());
return std::is_sorted(a.begin(), mit)
&& std::is_sorted(mit, a.end(), std::greater<int>());
}
int len(const std::pair<int,int>& p) {
return p.second - p.first + 1;
}
bool can_be_median(int cnt_less, int cnt_equal, int cnt_greater) {
return cnt_equal + cnt_less >= cnt_greater;
}
int sub3(const vector<int>& a) {
int n = SZ(a);
unordered_map<int, vector<pair<int,int>>> pos;
int l = 0;
while (l < n) {
int r = l;
while (r < n && a[l] == a[r]) ++r;
pos[a[l]].emplace_back(l, r-1);
l = r;
}
int res = 0;
for (const auto& [val, lrs] : pos) {
// only 1 segment
for (const auto& lr : lrs) res = max(res, len(lr));
// 2 segments
if (SZ(lrs) < 2) continue;
assert(SZ(lrs) == 2);
int cnt_equal = len(lrs[0]) + len(lrs[1]);
int cnt_greater = len({lrs[0].second + 1, lrs[1].first - 1});
int cnt_less = len({0, lrs[0].first - 1}) + len({lrs[1].second + 1, n-1});
if (can_be_median(cnt_less, cnt_equal, cnt_greater)) {
res = max(res, cnt_equal);
}
}
return res;
}
// SegTree, copied from AtCoder library {{{
// AtCoder doc: https://atcoder.github.io/ac-library/master/document_en/segtree.html
//
// Notes:
// - Index of elements from 0 -> n-1
// - Range queries are [l, r-1]
//
// Tested:
// - (binary search) https://atcoder.jp/contests/practice2/tasks/practice2_j
// - https://oj.vnoi.info/problem/gss
// - https://oj.vnoi.info/problem/nklineup
// - (max_right & min_left for delete position queries) https://oj.vnoi.info/problem/segtree_itstr
// - https://judge.yosupo.jp/problem/point_add_range_sum
// - https://judge.yosupo.jp/problem/point_set_range_composite
int ceil_pow2(int n) {
int x = 0;
while ((1U << x) < (unsigned int)(n)) x++;
return x;
}
template<
class T, // data type for nodes
T (*op) (T, T), // operator to combine 2 nodes
T (*e)() // identity element
>
struct SegTree {
SegTree() : SegTree(0) {}
explicit SegTree(int n) : SegTree(vector<T> (n, e())) {}
explicit SegTree(const vector<T>& v) : _n((int) v.size()) {
log = ceil_pow2(_n);
size = 1<<log;
d = vector<T> (2*size, e());
for (int i = 0; i < _n; i++) d[size+i] = v[i];
for (int i = size - 1; i >= 1; i--) {
update(i);
}
}
// 0 <= p < n
void set(int p, T x) {
assert(0 <= p && p < _n);
p += size;
d[p] = x;
for (int i = 1; i <= log; i++) update(p >> i);
}
// 0 <= p < n
T get(int p) const {
assert(0 <= p && p < _n);
return d[p + size];
}
// Get product in range [l, r-1]
// 0 <= l <= r <= n
// For empty segment (l == r) -> return e()
T prod(int l, int r) const {
assert(0 <= l && l <= r && r <= _n);
T sml = e(), smr = e();
l += size;
r += size;
while (l < r) {
if (l & 1) sml = op(sml, d[l++]);
if (r & 1) smr = op(d[--r], smr);
l >>= 1;
r >>= 1;
}
return op(sml, smr);
}
T all_prod() const {
return d[1];
}
// Binary search on SegTree to find largest r:
// f(op(a[l] .. a[r-1])) = true (assuming empty array is always true)
// f(op(a[l] .. a[r])) = false (assuming op(..., a[n]), which is out of bound, is always false)
template <bool (*f)(T)> int max_right(int l) const {
return max_right(l, [](T x) { return f(x); });
}
template <class F> int max_right(int l, F f) const {
assert(0 <= l && l <= _n);
assert(f(e()));
if (l == _n) return _n;
l += size;
T sm = e();
do {
while (l % 2 == 0) l >>= 1;
if (!f(op(sm, d[l]))) {
while (l < size) {
l = (2 * l);
if (f(op(sm, d[l]))) {
sm = op(sm, d[l]);
l++;
}
}
return l - size;
}
sm = op(sm, d[l]);
l++;
} while ((l & -l) != l);
return _n;
}
// Binary search on SegTree to find smallest l:
// f(op(a[l] .. a[r-1])) = true (assuming empty array is always true)
// f(op(a[l-1] .. a[r-1])) = false (assuming op(a[-1], ..), which is out of bound, is always false)
template <bool (*f)(T)> int min_left(int r) const {
return min_left(r, [](T x) { return f(x); });
}
template <class F> int min_left(int r, F f) const {
assert(0 <= r && r <= _n);
assert(f(e()));
if (r == 0) return 0;
r += size;
T sm = e();
do {
r--;
while (r > 1 && (r % 2)) r >>= 1;
if (!f(op(d[r], sm))) {
while (r < size) {
r = (2 * r + 1);
if (f(op(d[r], sm))) {
sm = op(d[r], sm);
r--;
}
}
return r + 1 - size;
}
sm = op(d[r], sm);
} while ((r & -r) != r);
return 0;
}
private:
int _n, size, log;
vector<T> d;
void update(int k) {
d[k] = op(d[2*k], d[2*k+1]);
}
};
// }}}
// SegTree examples {{{
// Examples: Commonly used SegTree ops: max / min / sum
struct MaxSegTreeOp {
static int op(int x, int y) {
return max(x, y);
}
static int e() {
return INT_MIN;
}
};
struct MinSegTreeOp {
static int op(int x, int y) {
return min(x, y);
}
static int e() {
return INT_MAX;
}
};
struct SumSegTreeOp {
static long long op(long long x, long long y) {
return x + y;
}
static long long e() {
return 0;
}
};
// using STMax = SegTree<int, MaxSegTreeOp::op, MaxSegTreeOp::e>;
// using STMin = SegTree<int, MinSegTreeOp::op, MinSegTreeOp::e>;
// using STSum = SegTree<int, SumSegTreeOp::op, SumSegTreeOp::e>;
// }}}
int sub4(const vector<int>& a) {
int n = SZ(a);
int res = 0;
int ln = *max_element(a.begin(), a.end());
for (int median = 0; median <= ln; ++median) {
vector<int> cnt_less(n, 0);
vector<int> cnt_equal(n, 0);
vector<int> cnt_greater(n, 0);
// [l, r] satisfies <=> cnt_less(l, r) + cnt_equal(l, r) - cnt_greater(l, r) >= 0
// Fix l => Find max r:
// cnt_less(l, r) + cnt_equal(l, r) - cnt_greater(l, r) >= 0
// <=> cnt_less[r] + cnt_equal[r] - cnt_greater[r]
// >= cnt_less[l-1] + cnt_equal[l-1] - cnt_greater[l-1]
for (int i = 0; i < n; ++i) {
cnt_less[i] = a[i] < median;
cnt_equal[i] = a[i] == median;
cnt_greater[i] = a[i] > median;
}
std::partial_sum(cnt_less.begin(), cnt_less.end(), cnt_less.begin());
std::partial_sum(cnt_equal.begin(), cnt_equal.end(), cnt_equal.begin());
std::partial_sum(cnt_greater.begin(), cnt_greater.end(), cnt_greater.begin());
// segment tree: stores max(r)
SegTree<int, MaxSegTreeOp::op, MaxSegTreeOp::e> st(2 * n + 1);
auto f = [&] (int i) {
// +n to make sure result >= 0
if (i < 0) return 0+n;
return cnt_less[i] + cnt_equal[i] - cnt_greater[i] + n;
};
for (int l = n-1; l >= 0; --l) {
int r = st.prod(f(l-1), 2*n + 1);
if (r > l) {
int equals = cnt_equal[r-1] - (l > 0 ? cnt_equal[l-1] : 0);
res = max(res, equals);
}
st.set(f(l), max(st.get(f(l)), l + 1));
}
}
return res;
}
int sequence(int n, std::vector<int> a) {
if (n <= 2000 || *max_element(a.begin(), a.end()) <= 3) return sub4(a);
if (is_sub_3(a)) return sub3(a);
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
0 ms |
212 KB |
Output is correct |
| 4 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
0 ms |
212 KB |
Output is correct |
| 4 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
141 ms |
31644 KB |
Output is correct |
| 3 |
Correct |
161 ms |
31688 KB |
Output is correct |
| 4 |
Correct |
35 ms |
6108 KB |
Output is correct |
| 5 |
Correct |
148 ms |
29104 KB |
Output is correct |
| 6 |
Correct |
145 ms |
29216 KB |
Output is correct |
| 7 |
Correct |
35 ms |
6084 KB |
Output is correct |
| 8 |
Correct |
38 ms |
6096 KB |
Output is correct |
| 9 |
Correct |
34 ms |
6100 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
212 KB |
Output is correct |
| 2 |
Correct |
288 ms |
22244 KB |
Output is correct |
| 3 |
Incorrect |
283 ms |
22200 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
51 ms |
6216 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
0 ms |
212 KB |
Output is correct |
| 4 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
0 ms |
212 KB |
Output is correct |
| 4 |
Incorrect |
1 ms |
212 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
