131 lines
3.2 KiB
Text
131 lines
3.2 KiB
Text
---
|
|
id: harder-ordered
|
|
title: "Harder Problems with Ordered Sets"
|
|
author: Benjamin Qi
|
|
prerequisites:
|
|
- Silver - Introduction to Ordered Sets
|
|
- Silver - Introduction to Stacks & Queues
|
|
description: ""
|
|
frequency: 2
|
|
---
|
|
|
|
import { Problem } from "../models";
|
|
|
|
export const metadata = {
|
|
problems: {
|
|
sample: [
|
|
new Problem("CSES", "Bit Inversions", "1188", "Normal", false, []),
|
|
],
|
|
general: [
|
|
new Problem("Silver", "Milk Measurement", "763", "Normal", false, []),
|
|
new Problem("Silver", "Convention II", "859", "Normal", false, []),
|
|
new Problem("Gold", "Snow Boots", "813", "Normal", false, []),
|
|
new Problem("CF", "Jury Marks", "contest/831/problem/C", "Hard", false, [], "Hard, would recommend skipping (1700 on CF)"),
|
|
new Problem("CF", "Mahmoud & Ehab & Function", "contest/862/problem/E", "Hard", false, [], "Hard, do not attempt until Gold/Plat (2100 on CF)"),
|
|
new Problem("CF", "Tournament", "contest/878/problem/C", "Very Hard", false, [], "First solve problem for $n$-th tournament only. Extremely hard, do not attempt (2700 on CF)"),
|
|
]
|
|
}
|
|
};
|
|
|
|
|
|
## Example: Using Iterators
|
|
|
|
<problems-list problems={metadata.problems.sample} />
|
|
|
|
<spoiler title="Solution">
|
|
|
|
```cpp
|
|
#include <bits/stdc++.h>
|
|
using namespace std;
|
|
|
|
#define sz(x) (x).size()
|
|
|
|
string s;
|
|
int m;
|
|
multiset<int> ans, ret;
|
|
|
|
void modify(int x) {
|
|
if (x == 0 || x == sz(s)) return;
|
|
auto it = ans.find(x);
|
|
if (it != end(ans)) {
|
|
int a = *prev(it), b = *next(it);
|
|
ret.erase(ret.find(x-a)), ret.erase(ret.find(b-x));
|
|
ret.insert(b-a);
|
|
ans.erase(it);
|
|
} else {
|
|
it = ans.insert(x);
|
|
int a = *prev(it), b = *next(it);
|
|
ret.erase(ret.find(b-a));
|
|
ret.insert(x-a), ret.insert(b-x);
|
|
}
|
|
}
|
|
|
|
int main() {
|
|
ios_base::sync_with_stdio(0); cin.tie(0);
|
|
cin >> s >> m;
|
|
ans.insert(0); ans.insert(sz(s));
|
|
for (int i = 0; i < sz(s)-1; ++i)
|
|
if (s[i] != s[i+1]) ans.insert(i+1);
|
|
for (auto it = ans.begin(); next(it) != ans.end(); it ++)
|
|
ret.insert(*next(it)-*it);
|
|
for (int i = 0; i < m; ++i) {
|
|
int x; cin >> x;
|
|
modify(x-1); modify(x);
|
|
cout << *ret.rbegin() << " ";
|
|
}
|
|
}
|
|
```
|
|
|
|
<br />
|
|
|
|
Note that `multiset` has a high constant factor, so replacing `ret` with an array and a `priority_queue` reduces the runtime by a factor of 2.
|
|
|
|
```cpp
|
|
#include <bits/stdc++.h>
|
|
using namespace std;
|
|
|
|
#define sz(x) (x).size()
|
|
|
|
string s;
|
|
int m;
|
|
set<int> ans;
|
|
priority_queue<int> ret;
|
|
int cnt[200005];
|
|
|
|
void ad(int x) { cnt[x] ++; ret.push(x); }
|
|
void modify(int x) {
|
|
if (x == 0 || x == sz(s)) return;
|
|
auto it = ans.find(x);
|
|
if (it != end(ans)) {
|
|
int a = *prev(it), b = *next(it); ans.erase(it);
|
|
cnt[x-a] --, cnt[b-x] --; ad(b-a);
|
|
} else {
|
|
it = ans.insert(x).first;
|
|
int a = *prev(it), b = *next(it);
|
|
cnt[b-a] --, ad(x-a), ad(b-x);
|
|
}
|
|
}
|
|
|
|
int main() {
|
|
ios_base::sync_with_stdio(0); cin.tie(0);
|
|
cin >> s >> m;
|
|
ans.insert(0); ans.insert(sz(s));
|
|
for (int i = 0; i < sz(s)-1; ++i)
|
|
if (s[i] != s[i+1]) ans.insert(i+1);
|
|
for (auto it = ans.begin(); next(it) != ans.end(); it ++)
|
|
ad(*next(it)-*it);
|
|
for (int i = 0; i < m; ++i) {
|
|
int x; cin >> x;
|
|
modify(x-1); modify(x);
|
|
while (!cnt[ret.top()]) ret.pop();
|
|
cout << ret.top() << " ";
|
|
}
|
|
}
|
|
```
|
|
|
|
</spoiler>
|
|
|
|
## Problems
|
|
|
|
<problems-list problems={metadata.problems.general} />
|