@[TOC](Codeforces Round 888 (Div. 3)（视频讲解全部题目）)

Codeforces Round 888 (Div. 3)（A–G）全部题目详解

A Escalator Conversations

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 1e5 + 10;

void solve()
{
	int n, m, k, H;
	cin >> n >> m >> k >> H;
	int ans = 0;
	for(int i = 0; i < n; i ++)
	{
		int h;
		cin >> h;
		int dis = abs(h - H);
		if(h != H && dis % k == 0 && dis / k < m)
			ans ++;
	}
	cout << ans << endl;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}

B Parity Sort

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 1e5 + 10;

void solve()
{
	int n;
	cin >> n;
	vector<int>a(n);
	for(int i = 0; i < n; i ++)
		cin >> a[i];
	vector<int>b;
	b = a;
	sort(b.begin(), b.end());
	for(int i = 0; i < n; i ++)
	{
		if(a[i] % 2 != b[i] % 2)
		{
			cout << "NO" << endl;
			return;
		}
	}
	cout << "YES" << endl;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}

C Tiles Comeback

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 1e5 + 10;

void solve()
{
	int n, k;
	cin >> n >> k;
	vector<int>a(n);
	for(int i = 0; i < n; i ++)
		cin >> a[i];
	if(a[0] == a.back())
	{
		if(count(a.begin(), a.end(), a[0]) >= k)
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	else
	{
		int c1 = count(a.begin(), a.end(), a[0]);
		int c2 = count(a.begin(), a.end(), a.back());
		int cnt = 0;
		for(int i = 0; i < n; i ++)
		{
			if(a[i] == a[0])
				cnt ++;
			if(a[i] == a.back())
				c2 --;
			if(cnt == k)
				break;
		}
		if(c1 >= k && c2 >= k)
		{
			cout << "YES" << endl;
		}
		else
		{
			cout << "NO" << endl;
		}
	}
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}

D Prefix Permutation Sums

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
#define int long long
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 1e5 + 10;

void solve()
{
	int n;
	cin >> n;
	vector<int>a(n - 1);
	for(int i = 0; i < n - 1; i ++)
		cin >> a[i];
	int sum = n * (n + 1) / 2;
	if(sum != a.back())
	{
		a.push_back(sum);

		map<int,bool>st;

		for(int i = 0; i < n; i ++)
		{
			int b;
			if(!i)
				b = a[i];
			else
				b = a[i] - a[i - 1];
			if(b <= 0 || b > n || st[b])
			{
				cout << "NO" << endl;
				return;
			}
			st[b] = true;
		}
		cout << "YES" << endl;
	}
	else
	{
		map<int,bool>st;
		int x, cnt = 0;
		for(int i = 0; i < n - 1; i ++)
		{
			int b;
			if(!i)
				b = a[i];
			else
				b = a[i] - a[i - 1];
			if(b <= 0 || b > 2 * n)
			{
				cout << "NO" << endl;
				return;
			}
			if(b > n || st[b])
			{
				x = b;
				cnt ++;
			}
			st[b] = true;
		}
		if(cnt > 1)
		{
			cout << "NO" << endl;
			return;
		}
		else
		{
			int sum = 0;
			int c = 0;
			for(int i = 1; i <= n; i ++)
			{
				if(!st[i])
				{
					sum += i;
					c ++;
				}
			}
			if(c == 2 && sum == x)
			{
				cout << "YES" << endl;
			}
			else
			{
				cout << "NO" << endl;
			}
		}
	}
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}

E Nastya and Potions

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
#define int long long
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 2e5 + 10;
int c[N], idx[N], ans[N];
map<int,bool>p;
int n, k;
vector<int>edge[N];

void bfs()
{
	queue<int>q;
	for(int i = 0; i < n; i ++)
	{
		if(idx[i] == 0)
		{
			q.push(i);
			if(p[i])
				ans[i] = 0;
			else
				ans[i] = c[i];
		}
	}

	while(q.size())
	{
		int t = q.front();
		q.pop();
		for(int i = 0; i < edge[t].size(); i ++)
		{
			int son = edge[t][i];
			ans[son] += ans[t];
			idx[son] --;
			if(idx[son] == 0)
			{
				if(p[son])
					ans[son] = 0;
				else
					ans[son] = min(ans[son], c[son]);
				q.push(son);
			}
		}

	}
}

void solve()
{

	cin >> n >> k;
	for(int i = 0; i < n; i ++)
	{
		c[i] = idx[i] = ans[i] = 0;
		edge[i].clear();
	}
	p.clear();
	for(int i = 0; i < n; i ++)
		cin >> c[i];
	for(int i = 0; i < k; i ++)
	{
		int x;
		cin >> x;
		x --;
		p[x] = true;
	}
	for(int i = 0; i < n; i ++)
	{
		int m;
		cin >> m;
		for(int j = 0; j < m; j ++)
		{
			int x;
			cin >> x;
			x --;
			idx[i] ++;
			edge[x].push_back(i);
		}
	}
	bfs();
	for(int i = 0; i < n; i ++)
		cout << ans[i] << " ";
	cout << endl;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}

F Lisa and the Martians

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 1e5 + 10;

void solve()
{
	int n, k;
	cin >> n >> k;
	vector<pii>a(n);

	for(int i = 0; i < n; i ++)
	{
		cin >> a[i].first;
		a[i].second = i + 1;
	}
	sort(a.begin(), a.end());
	int minv = INT_MAX, a1, a2, p1, p2;
	for(int i = 0; i < n - 1; i ++)
	{
		if(minv > (a[i].first ^ a[i + 1].first))
		{
			a1 = a[i].first, a2 = a[i + 1].first;
			p1 = a[i].second, p2 = a[i + 1].second;
			minv = a1 ^ a2;
		}
	}
	int x = 0;
	for(int i = 0; i < k; i ++)
	{
		int x1 = (a1 >> i) & 1, x2 = (a2 >> i) & 1;
		if(x1 + x2 == 0)
			x += 1 << i;
	}
	cout << p1 << " " << p2 << " " << x << endl;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}

G Vlad and the Mountains

#include<bits/stdc++.h>
#define endl '\n'
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int N = 2e5 + 10;
int h[N], p[N];
struct NODE
{
	int a, b, w;
};
struct QRY
{
	int a, b, h_max, ii;
};
vector<NODE>edge;
vector<QRY>Q;
bool cmp1(NODE x, NODE y)
{
	return x.w < y.w;
}
bool cmp2(QRY x, QRY y)
{
	return x.h_max < y.h_max;
}

int find(int x)
{
	if(x != p[x])
		p[x] = find(p[x]);
	return p[x];
}
void solve()
{
	edge.clear();
	Q.clear();
	int n, m;
	cin >> n >> m;
	for(int i = 1; i <= n; i ++)
		cin >> h[i];
	for(int i = 0; i < m; i ++)
	{
		int a, b;
		cin >> a >> b;
		edge.push_back({a,b, max(h[a], h[b])});
	}
	sort(edge.begin(), edge.end(), cmp1);
	int q;
	cin >> q;
	vector<bool>ans(q);
	for(int i = 0; i <= n; i ++)
		p[i] = i;

	for(int i = 0; i < q; i ++)
	{
		int a, b, e;
		cin >> a >> b >> e;
		Q.push_back({a, b, h[a] + e, i});
	}
	sort(Q.begin(), Q.end(), cmp2);
	int cnt = 0;
	for(int i = 0; i < q; i ++)
	{
		while(cnt < m && Q[i].h_max >= edge[cnt].w)
		{
			int pa = find(edge[cnt].a), pb = find(edge[cnt].b);
			if(pa != pb)
				p[pa] = pb;
			cnt ++;
		}
		if(find(Q[i].a) == find(Q[i].b))
			ans[Q[i].ii] = true;
		else
			ans[Q[i].ii] = false;
	}
	for(int i = 0; i < q; i ++)
	{
		if(ans[i])
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	cout << endl;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while(t--)
	solve();
}