Submission #384153

#	Time	Username	Problem	Language	Result	Execution time	Memory
384153		dapig	Network (BOI15_net)	C++11	100 / 100	919 ms	63364 KiB

net

#include <cstdio>
#include <iostream> 
#include <vector>
#include <queue>
#include <algorithm>
#include <set>
#include <map>
#include <utility>

using namespace std;

int n;
vector<int> graph[500005];
int start;
	
	int leaves[500005];
	int et[500005]; int marker = 0;
	int etrev[500005];
	
int bit[500005];
void upd(int n, int inc) {
	n++;
	while (n < 500005) {
			bit[n] += inc;
			n += (n&-n);
		}
	}
	int find(int n) {
		int s = 0;
		n++;
		while (n > 0) {
			s += bit[n];
			n -= (n&-n);
		}
		return s;
	}
	int findfirst(int n) {
		if (graph[n].size()==1) return etrev[n];
		int l = 0, r = 500005, v = find(etrev[n]);
		int best = 500004;
		while (l < r) {
			int m = (l+r)/2;
			if (find(m) > v) {
				best = m; r = m;
			} else l = m+1;
		}
		return best;
	}
	int leaffind(int n, int p) {
		et[marker] = n; marker++;
		etrev[et[marker-1]] = marker-1;
		int vis = 0;
		for (int i : graph[n]) {
			if (i == p) continue;
			vis += leaffind(i, n);
		}
		if (vis == 0) {
			leaves[n] = 1;
			upd(marker-1, 1);
			return 1;
		}
		leaves[n] = vis;
		return vis;
	}
	
	vector<pair<int, int>> pairs;
	void findans(int n, int p, int reps) {
		int max = 0, pos = 0, sum = 0;
		for (int i : graph[n]) {
			if (i == p) continue;
			sum += leaves[i];
			if (leaves[i] > max) {
				max = leaves[i];
				pos = i;
			}
		}
		int pairable = min(sum, (sum-max)*2);
		if (reps > pairable) {
			findans(pos, n, reps-pairable);
			leaves[pos] = sum-max;
			reps -= (reps-pairable);
		}
		/*
		PriorityQueue<int[]> pq = new PriorityQueue<>(new SortArr());
		for (int i : graph[n]) {
			if (i == p) continue;
			pq.add(new int[] {i, leaves[i]});
		}
		
		while (reps > 1) {
			int[] data1 = pq.poll();
			int[] data2 = pq.poll();
			int pos1 = findfirst(data1[0]);
			int pos2 = findfirst(data2[0]);
			upd(pos1, -1); upd(pos2, -1);
			pairs.add(new int[] {et[pos1]+1, et[pos2]+1});
			if (data1[1] > 1) pq.add(new int[] {data1[0], data1[1]-1});
			if (data2[1] > 1) pq.add(new int[] {data2[0], data2[1]-1});
			reps -= 2;
		}
		
		if (reps == 1) {
			int[] data1 = pq.poll();
			int pos1 = findfirst(data1[0]);
			upd(pos1, -1);
			pairs.add(new int[] {et[pos1]+1, n+1});
		}*/
		int maxleaves = 0;
		for (int i : graph[n]) {
			if (i==p) continue;
			maxleaves = std::max(maxleaves, leaves[i]);
		}
		vector<int> stack[maxleaves+1];
		for (int i = 0; i < maxleaves+1; i++) {
			vector<int> temp;
            stack[i] = temp;
		}
		max = 0; int max2 = 0;
		for (int i : graph[n]) {
			if (i==p) continue;
			stack[leaves[i]].push_back(i);
			if (leaves[i] > max) {
				max2 = max; max = leaves[i];
			} else if (leaves[i] > max2) max2 = leaves[i];
		}
		while (reps > 1) {
			pair<int, int> data1{stack[max].back(), max};
			stack[max].pop_back();
			pair<int, int> data2{stack[max2].back(), max2};
            stack[max2].pop_back();
			int pos1 = findfirst(data1.first);
			int pos2 = findfirst(data2.first);
			upd(pos1, -1); upd(pos2, -1);
			pairs.push_back({et[pos1]+1, et[pos2]+1});
			if (data1.second > 1) {
				stack[data1.second-1].push_back(data1.first);
			}
			if (data2.second > 1) {
				stack[data2.second-1].push_back(data2.first);
			}
			if (stack[max].size() == 0) max--;
			if (stack[max2].size() == 0) max2--;
			if (max2 == max && stack[max].size() == 1) max2--;
			reps -= 2;
		}
		if (reps == 1) {
			pair<int, int> data1{stack[max].back(), max};
            stack[max].pop_back();
			int pos1 = findfirst(data1.first);
			upd(pos1, -1);
			pairs.push_back({et[pos1]+1, n+1});
		}
	}
	
	int main() {

		cin >> n;
		for (int i = 0; i < 500005; i++) {
            vector<int> temp;
			graph[i] = temp;
		}
		for (int i = 0; i < n-1; i++) {
			int a, b; cin >> a >> b; a--; b--;
			graph[a].push_back(b);
			graph[b].push_back(a);
		}
		
		for (int i = 0; i < 500005; i++) {
			if (graph[i].size() > 1) {
				start = i; break;
			}
		}
		leaffind(start, -1);
		findans(start, -1, leaves[start]);
		cout << (pairs.size()) << "\n";
		for (pair<int, int> i : pairs) {
			cout << (i.first) << " " << (i.second) << "\n";
		}

	}

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 37 / 37