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Codeforces-solutions/Hello 2023/C. Least Prefix Sum.cpp
2026-03-17 15:17:32 -03:00

161 lines
2.9 KiB
C++

/* Problem URL: https://codeforces.com/problemset/problem/1779/C */
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T, class comp = less<>>
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
#define V vector
#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)
#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;
template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
os << vec[0];
for (size_t i = 1; i < vec.size(); i++) {
os << ' ' << vec[i];
}
os << '\n';
return os;
}
template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
for (auto &i : vec) {
is >> i;
}
return is;
}
template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
for (auto &i : vec) {
os << i[0];
for (size_t j = 1; j < i.size(); j++) {
os << ' ' << i[j];
}
os << '\n';
}
return os;
}
template<class v>
auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
for (auto &i : vec) {
for (auto &j : i) {
is >> j;
}
}
return is;
}
const int oo = INT32_MAX >> 1;
const ll OO = INT64_MAX >> 1;
void pre()
{
}
#define TEST 1
void solve()
{
int n, m;
cin >> n >> m;
vl a(n);
cin >> a;
m--;
int ans = 0;
vl pref(n + 1);
nrep(i, 1, n + 1) {
pref[i] = pref[i - 1] + a[i - 1];
}
pref[0] = OO;
priority_queue<pair<ll, int>> pq;
ll cur = pref[m + 1];
for (int i = m; i >= 0; i--) {
pq.emplace(a[i], i);
while (cur > pref[i]) {
auto [c, j] = pq.top();
pq.pop();
a[j] = -a[j];
cur -= c * 2;
ans++;
}
}
while (!pq.empty()) {
pq.pop();
}
pref[0] = 0;
nrep(i, 1, n + 1) {
pref[i] = pref[i - 1] + a[i - 1];
}
priority_queue<ll, vl, greater<>> mpq;
cur = pref[m + 1];
nrep(i, m + 1, n) {
cur += a[i];
mpq.push(a[i]);
while (cur < pref[m + 1]) {
cur -= mpq.top() * 2;
mpq.pop();
ans++;
}
}
cout << ans << '\n';
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
pre();
int t;
(TEST && cin >> t) || (t = 1);
while (t--) {
solve();
}
}