Submission #836272

#	Time	Username	Problem	Language	Result	Execution time	Memory
836272		gustason	City Mapping (NOI18_citymapping)	C++14	22 / 100	130 ms	10376 KiB

citymapping

#include <bits/stdc++.h>
#include "citymapping.h"
using namespace std;

const int nax = 1002;

struct Dsu {
	int par[nax];
	int sz[nax];
	
	Dsu() {
		for(int i = 0; i < nax; i++) {
			par[i] = i;
			sz[i] = 1;
		}
	}
	
	int find(int v) {
		if (v == par[v]) {
			return v;
		}
		return par[v] = find(par[v]);
	}
	
	bool unite(int a, int b) {
		 a = find(a), b = find(b);
		 if (a == b) return false;
		 
		 if (sz[b] > sz[a]) swap(a, b);
		 par[b] = a;
		 sz[a] += sz[b];
		 return true;
	}
};

int dist[nax][nax];

int get_dist(int a, int b) {
	if (dist[a][b] != 0) {
		return dist[a][b];
	}
	return dist[a][b] = get_distance(a, b);
}

void brute(int N, int* A, int* B, int* W) {
	vector<array<int, 3>> d;
	for(int i = 1; i <= N; i++) {
		for(int j = i+1; j <= N; j++) {
			get_dist(i, j);
			d.push_back({dist[i][j], i, j});
		}
	}
	
	sort(d.begin(), d.end());
	Dsu dsu;
	
	int idx = 0;
	for(auto& i : d) {
		if (dsu.unite(i[1], i[2])) {
			A[idx] = i[1];
			B[idx] = i[2];
			W[idx] = i[0];
			idx++;
		}
	}
}

void find_roads(int N, int Q, int A[], int B[], int W[]) {
	if (Q == 500000) {
		brute(N, A, B, W);
		return;
	}
	vector<array<int, 2>> d;
	for(int i = 2; i <= N; i++) {
		d.push_back({get_dist(1, i), i});
	}
		
	sort(d.begin(), d.end());
	
	//for(auto& i : d) {
		//cout << i[0] << " " << i[1] << "\n";
	//}
	
	A[0] = 1, B[0] = d[0][1], W[0] = d[0][0];
	if (N == 2) return;
		
	vector<int> child{B[0]};
		
	for(int i = 1; i < N-1; i++) {
		bool found = false;
		for(int& u : child) {
			if (d[i][0] == get_dist(1, u) + get_dist(u, d[i][1])) {
				found = true;
				A[i] = u;
				B[i] = d[i][1];
				u = B[i];
				break;
			}
		}
				
		if (!found) {
			A[i] = 1;
			B[i] = d[i][1];
			child.push_back(B[i]);
			assert(get_dist(1, d[i][1]) == d[i][0]);
		}
		
		W[i] = get_dist(A[i], B[i]);
	}
	
	//for(int i = 0; i < N; i++) {
		//cout << A[i] << " " << B[i] << " " << W[i] << "\n";
	//}
	
	//for(auto& i : d) {
		//cout << i[0] << " " << i[1] << "\n";
	//}
	return;
}

• Subtask 1: 9 / 9
• Subtask 2: 0 / 16
• Subtask 3: 13 / 13
• Subtask 4: 0 / 19
• Subtask 5: 0 / 43