Submission #532271

#	Time	Username	Problem	Language	Result	Execution time	Memory
532271		sidon	Ideal city (IOI12_city)	C++17	100 / 100	607 ms	61744 KiB

city

#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;

const array<int, 2> mv[4] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};

const int Z = 1e5;

int n, s[Z];
map<int, int> toS[Z];
set<int> g[Z], h[Z];

void dfs(int u, int p) {
	for(const int &v : g[u]) if(v != p) {
		dfs(v, u);
		s[u] += toS[u][v] = s[v];
		toS[v][u] = n - s[v];
	}
}

i64 curSum, ans;

void cnt(int u) {
	s[u] = 1;
	ans += curSum;
	for(const int &v : h[u]) if(!s[v]) {
		curSum += i64(n - 2 * toS[u][v]);
		cnt(v);
		curSum -= i64(n - 2 * toS[u][v]);
	}
}

int DistanceSum(int N, int *X, int *Y) {

	map<int, map<int, int>> cAt;

	int o[N], id[N]; n = N;
	for(int i = 0; i < N; ++i)
		cAt[X[i]][Y[i]] = (o[i] = i) + 1;

	for(int u = 0; u < N; ++u) {
		for(const auto &[dx, dy] : mv) {
			int v = cAt[X[u] + dx][Y[u] + dy] - 1;
			if(v >= 0) h[u].insert(v);
		}
	}

	for(int _ = 0; _ < 2; ++_) {
		if(_) {
			cAt.clear();
			for(int i = 0; i < N; ++i)
				cAt[X[i]][Y[i]] = i + 1;
		}

		sort(o, o + N, [&](const int &i, const int &j) {
			return Y[i] < Y[j];
		});

		for(const int &u : o) {
			int v = cAt[X[u]][Y[u] - 1] - 1;
			id[u] = v < 0 ? u : id[v];
		}

		fill(s, s + N, 0);
		fill(g, g + N, set<int> ());

		for(int u = 0; u < N; ++u) {
			++s[id[u]];
			for(const int &v : h[u]) if(id[u] != id[v])
				g[id[u]].insert(id[v]);
		}

		dfs(id[0], id[0]);

		for(int u = 0; u < N; ++u)
			for(const int &v : h[u]) if(id[u] != id[v])
				toS[u][v] = toS[id[u]][id[v]];

		swap(X, Y);
	}

	queue<pair<int, int>> q;
	bool vis[N] {1};
	q.emplace(0, 0);

	while(!empty(q)) {
		auto [u, d] = q.front(); q.pop();
		curSum += i64(d);

		for(const int &v : h[u])
			if(v >= 0 && !vis[v])
				vis[v] = 1, q.emplace(v, d + 1);
	}

	fill(s, s + N, 0);
	cnt(0);

	return (ans >> 1) % i64(1e9);
}

• Subtask 1: 11 / 11
• Subtask 2: 21 / 21
• Subtask 3: 23 / 23
• Subtask 4: 45 / 45