125 lines
3.2 KiB
C++
125 lines
3.2 KiB
C++
/* Problem URL: https://codeforces.com/edu/course/2/lesson/4/2/practice/contest/273278/problem/A */
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#include <bits/stdc++.h>
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using namespace std;
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#define V vector
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#define rmin(a, b) a = min(a, b)
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#define rmax(a, b) a = max(a, b)
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#define rep(i, lim) for (size_t i = 0; i < (lim); i++)
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#define nrep(i, s, lim) for (size_t i = s; i < (lim); i++)
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#define repv(i, v) for (auto &i : (v))
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#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
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#define sortv(v) sort(v.begin(), v.end())
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#define all(v) (v).begin(), (v).end()
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using vi = vector<int>;
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using vvi = vector<vi>;
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using vvvi = vector<vvi>;
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using vvvvi = vector<vvvi>;
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using ll = long long;
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using vl = vector<ll>;
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using vvl = vector<vl>;
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using vvvl = vector<vvl>;
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using vvvvl = vector<vvvl>;
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template<class v>
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auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
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os << vec[0];
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for (size_t i = 1; i < vec.size(); i++) {
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os << ' ' << vec[i];
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}
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os << '\n';
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<v> &vec)->istream& {
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for (auto &i : vec) {
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is >> i;
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}
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return is;
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}
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template<class v>
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auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
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for (auto &i : vec) {
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os << i[0];
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for (size_t j = 1; j < i.size(); j++) {
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os << ' ' << i[j];
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}
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os << '\n';
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}
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
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for (auto &i : vec) {
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for (auto &j : i) {
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is >> j;
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}
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}
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return is;
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}
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struct node {
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ll ans;
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ll sum;
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ll pref;
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ll suf;
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node(ll ans, ll sum, ll pref, ll suf): ans(ans), sum(sum), pref(pref), suf(suf) {}
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node() = default;
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};
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V<node> segtree;
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int main()
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{
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ios::sync_with_stdio(false);
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cin.tie(nullptr);
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int n, m;
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cin >> n >> m;
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vl ar(n);
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cin >> ar;
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while (__builtin_popcount(n) != 1) {
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ar.push_back(-1);
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n++;
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}
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segtree.resize(n * 2);
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for (size_t i = n; i < n * 2; i++) {
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segtree[i] = node(max(ar[i - n], 0LL), ar[i - n], max(ar[i - n], 0LL), max(ar[i - n], 0LL));
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}
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for (size_t i = n - 1; i > 0; i--) {
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segtree[i].ans = max(segtree[i * 2].suf + segtree[i * 2 + 1].pref, max(segtree[i * 2].ans, segtree[i * 2 + 1].ans));
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segtree[i].sum = segtree[i * 2].sum + segtree[i * 2 + 1].sum;
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segtree[i].pref = max(segtree[i * 2].pref, segtree[i * 2].sum + segtree[i * 2 + 1].pref);
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segtree[i].suf = max(segtree[i * 2 + 1].suf, segtree[i * 2 + 1].sum + segtree[i * 2].suf);
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}
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cout << segtree[1].ans << '\n';
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while (m--) {
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ll i, v;
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cin >> i >> v;
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segtree[n + i] = node(max(v, 0LL), v, max(v, 0LL), max(v, 0LL));
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for (size_t j = (n + i) / 2; j > 0; j /= 2) {
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segtree[j].ans = max(segtree[j * 2].suf + segtree[j * 2 + 1].pref, max(segtree[j * 2].ans, segtree[j * 2 + 1].ans));
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segtree[j].sum = segtree[j * 2].sum + segtree[j * 2 + 1].sum;
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segtree[j].pref = max(segtree[j * 2].pref, segtree[j * 2].sum + segtree[j * 2 + 1].pref);
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segtree[j].suf = max(segtree[j * 2 + 1].suf, segtree[j * 2 + 1].sum + segtree[j * 2].suf);
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}
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cout << segtree[1].ans << '\n';
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}
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}
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