25普及联考day6爆炸记

省流：弘文。

一共四个题。大概开考后 20min 过了 T1, T2, T3。然后仔细想了想发现 T2 读错题了。改了 30min 才改出来，中间去水了一会 QQ。

然后想 T4，很快想出解法，然后开始写了。

然后一直写到比赛结束，写了 5K？？？？？为了防止自己以后再犯这种神志不清的错误，这里放一下考场错误仅有 15pts 代码来警示自己。

/*
Solution:

*/
#include <bits/stdc++.h>

using ll = long long;
using ull = unsigned long long;
//using i28 = __int128_t;
//using u28 = __uint128_t;
using ldb = long double;

#define int long long
#define max(x, y) (x > y ? x : y)
#define min(x, y) (x < y ? x : y)
#define abs(x) (x < 0 ? -x : x)

constexpr int N = 5e5 + 10;
int n, m, Xcnt, q;

int anc[N], sz[N]; 
int find(int u) {
	if (anc[u] == u) return u;
	else return anc[u] = find(anc[u]); 
}
void merge(int u, int v) {
	u = find(u), v = find(v);
	if (u != v) sz[v] += sz[u], anc[u] = v; 
}

int rid[N];
struct node {
	int sz; std::vector <int> vec;
	bool operator < (const node &cmp) const {
		return sz > cmp.sz; 
	}
} a[N]; 
std::vector <int> vec[N];  

signed main() {
//	freopen(".in", "r", stdin), freopen(".out", "w", stdout);
	std::ios::sync_with_stdio(false), std::cin.tie(nullptr), std::cout.tie(nullptr);

	std::cin >> n >> m >> Xcnt >> q;
	for (int i = 1; i <= n; ++i) {
		anc[i] = i, sz[i] = 1; 
	}
	while (q --> 0) {
		int _u, _v; std::cin >> _u >> _v;
		merge(_v, _u); 
	}
	if (m > (n - 1) * n) {
		return std::cout << "-1\n", 0; 
	}
	int tmp = 0, tmp2 = 0, tot = 0;
	for (int i = 1; i <= n; ++i) if (find(i) == i) {
		tmp += (sz[i] == 1 ? 0 : sz[i]), a[++tot].sz = sz[i], rid[i] = tot, a[tot].vec.emplace_back(i);
	} else a[rid[find(i)]].vec.emplace_back(i);
	if (tmp > m || tot < Xcnt) {
		return std::cout << "-1\n", 0; 
	} m -= tmp; 
	std::sort(a + 1, a + 1 + tot);
	if (m < 0) {
		return std::cout << "-1", 0;
	}
	// merge to Xcnt connected blocks with no cost
//	for (int i = 1; i <= tot; ++i) {
//		std::cout << a[i].sz << " : "; for (auto j : a[i].vec) std::cout << j << " "; std::cout << "\n";
//	}
	int new_sz = a[1].sz;
	std::vector <int> new_vec = a[1].vec; 
	for (int i = 2; i <= tot - Xcnt + 1; ++i) { // merge i and i - 1
		if (new_sz == 1) --m; if (a[i].sz == 1) --m; 
		new_sz += a[i].sz;
		for (auto j : a[i].vec) new_vec.emplace_back(j); 
//		std::cout << i << "\n";
	}
	if (m < 0) return std::cout << "-1\n", 0;
	a[1].sz = new_sz, a[1].vec = new_vec;
	int pos = 1; 
	for (int i = tot - Xcnt + 2; i <= tot; ++i) a[++pos] = a[i];
	for (int i = Xcnt + 1; i <= tot; ++i) a[i].sz = 0, a[i].vec.clear(); 
	
//	std::cout << m << "\n";
//	for (int i = 1; i <= Xcnt; ++i) {
//		std::cout << a[i].sz << " : ";
////		for (auto j : a[i].vec) std::cout << j << " "; std::cout << "\n";
//		for (int j = 0; j < a[i].vec.size(); ++j) std::cout << a[i].vec[j] << " "; std::cout << "\n";
//	}
//	std::cout << m << "\n";
	
	// check
	tmp = 0;
	int tmpm = m; 
	for (int i = 1; i <= Xcnt; ++i) {
		int cur = (a[i].sz - 1) * a[i].sz - a[i].sz;
		tmpm -= cur; 
	}
	int cursz = a[1].sz;
	for (int i = 2; i <= Xcnt; ++i) {
		int cur = cursz * a[i].sz;
		tmpm -= cur, cursz += a[i].sz; 
	}
	if (tmpm > 0) {
		return std::cout << "-1\n", 0; 
	}
	//
	
	for (int i = 1; i <= Xcnt; ++i) {
		for (int j = 0; j < a[i].vec.size() - 1; ++j) {
			std::cout << a[i].vec[j] << " " << a[i].vec[j + 1] << "\n"; 
		}
		if (a[i].sz > 1) std::cout << a[i].vec.back() << " " << a[i].vec.front() << "\n"; 
	}
	for (int i = 1; i <= Xcnt; ++i) {
		int cur = (a[i].sz - 1) * a[i].sz - a[i].sz;
		if (m <= cur) {
			for (int j = 1; j < i; ++j) {
				for (int k = 0; k < a[j].vec.size(); ++k) for (int h = 0; h < a[j].vec.size(); ++h) if (k != h) {
					if (h == k + 1) continue ;
					if (k == 0 && h == a[j].vec.size() - 1) continue ; 
					std::cout << a[j].vec[k] << " " << a[j].vec[h] << "\n"; 
				}
			}
			int p = 0;
			while (m > 0) {
				for (int j = 0; j < a[i].vec.size(); ++j)
					if (p != j) {
						if (p != j + 1 && !(j == a[i].vec.size() - 1 && p == 0)) {
							std::cout << a[i].vec[j] << " " << a[i].vec[p] << "\n";
							--m;
							if (m == 0) break ; 
						}
						if (j != p + 1 && !(p == a[i].vec.size() - 1 && j == 0)) {
							std::cout << a[i].vec[p] << " " << a[i].vec[j] << "\n";
							--m;  
							if (m == 0) break ; 
						}
					}
				++p; 
			}
			return 0; 
		}
		m -= cur; 
	}
	int cur_sz = a[1].sz;
	for (int i = 2; i <= Xcnt; ++i) { // merge i and i - 1
		int add = a[i].sz * cur_sz;
		if (m <= add) {
			std::vector <int> ans;
			for (int j = 1; j <= Xcnt; ++j) {
				for (int k = 0; k < a[j].vec.size(); ++k) for (int h = 0; h < a[j].vec.size(); ++h) 
					if (h != k) {
						if (h != k + 1 && !(k == a[j].vec.size() - 1 && h == 0)) std::cout << a[j].vec[k] << " " << a[j].vec[h] << "\n";
						if (k != h + 1 && !(h == a[j].vec.size() - 1 && k == 0)) std::cout << a[j].vec[h] << " " << a[j].vec[k] << "\n";
					}
			}
			for (int j = 1; j < i; ++j) for (auto k : a[j].vec) ans.emplace_back(k);
//			for (auto j : ans) for (auto k : ans) if (j != k) std::cout << j << " " << k << "\n";
			for (int j = 1; j < i; ++j) {
				for (int k = j + 1; k < i; ++k)
					for (auto a1 : a[j].vec) for (auto a2 : a[j].vec) std::cout << a1 << " " << a2 << "\n"; 
			}
			int p = 0; 
			while (m > 0) {
				for (auto j : a[i].vec) {
					std::cout << ans[p] << " " << j << "\n";
					--m; if (m == 0) break ; 
					std::cout << j << " " << ans[p] << "\n"; 
					--m; 
				} ++p; 
			}
			return 0;
		} m -= add, cur_sz += a[i].sz; 
	}
	std::cout << "-1\n"; 
	return 0;
}

大概是不知道自己写了什么。

比赛成绩出来是 \(100 + 90 + 100 + 15\)，预计是 \(100 + 100 + 100 + [0, 100]\)。自闭了。