AtCoder Regular Contest 189 (Div. 2)

A

计数

B

折叠差不变

D

观察性质暴力

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define endl '\n'
#define LL long longconst int N = 5e5 + 10;
int n, a[N], l[N], r[N];
LL pre[N], suf[N], b[N];void solve() {cin >> n;for (int i = 1; i <= n; i++) {cin >> a[i];b[i] = a[i];l[i] = i - 1; r[i] = i + 1;pre[i] = pre[i - 1] + a[i];}for (int i = n; i >= 1; i--) {suf[i] = suf[i + 1] + a[i];}while (1) {bool flag = 0;for (int i = 1; i <= n; i++) {while (l[i] >= 1 && b[i] > a[l[i]]) {b[i] += pre[l[i]] - pre[l[l[i]]];l[i] = l[l[i]];flag = 1;}}for (int i = n; i >= 1; i--) {while (r[i] <= n && b[i] > a[r[i]]) {b[i] += suf[r[i]] - suf[r[r[i]]];r[i] = r[r[i]];flag = 1;}}if (!flag) break;}for (int i = 1; i <= n; i++) {cout << b[i] << ' ';}
}int main() {// ios::sync_with_stdio(false);// cin.tie(nullptr);// cin >> t;solve();return 0;
}

笛卡尔树（特殊）

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define endl '\n'
#define LL long longconst int N = 5e5 + 10;
int n, a[N], ls[N], rs[N], k, stk[N];
LL ans[N], sum[N];
void dfs1(int x) {sum[x] = a[x];if (ls[x]) dfs1(ls[x]);if (rs[x]) dfs1(rs[x]);if (ls[x]) sum[x] += sum[ls[x]];if (rs[x]) sum[x] += sum[rs[x]];
}
void dfs(int x, int fa) {ans[x] = sum[x];if (fa && ans[x] > a[fa]) ans[x] = ans[fa];if (ls[x]) dfs(ls[x], x);if (rs[x]) dfs(rs[x], x);
}void solve() {int top = 0;cin >> n;for (int i = 1; i <= n; i++) {cin >> a[i];while(k > 0 && a[stk[k]] < a[i]) k--;if (k) rs[stk[k]] = i;if (k < top) ls[i] = stk[k + 1];stk[++k] = i;top = k;}dfs1(stk[1]);dfs(stk[1], 0);a[0] = a[n + 1] = 1e9 + 7;for (int i = 1; i <= n; i++) {if (a[i - 1] < a[i] || a[i] > a[i + 1]) cout << ans[i] << ' ';else cout << a[i] << ' ';}
}int main() {ios::sync_with_stdio(false);cin.tie(nullptr);// cin >> t;solve();return 0;
}