Submission #24513

#	Time	Username	Problem	Language	Result	Execution time	Memory
24513		Bruteforceman	Network (BOI15_net)	C++11	0 / 100	3 ms	17648 KiB

net

#include "bits/stdc++.h"
using namespace std;
int deg[500010];
deque <int> nodes; 
vector <int> g[500010];

int sub[500010];

void leaf(int x, int par) {
	if(deg[x] == 1) sub[x] = 1;
	else sub[x] = 0;
	for(auto i : g[x]) {
		if(i - par) {
			leaf(i, x);
			sub[x] += sub[i];
		}
	}
}

bool comp(int x, int y) {
	return sub[x] > sub[y];
}

void dfs(int x, int par) {
	if(deg[x] == 1) {
		nodes.push_back(x);
	}
	sort(g[x].begin(), g[x].end(), comp);
	for(auto i : g[x]) {
		if(i - par) {
			dfs(i, x);		
		} 
	}
}

int main(int argc, char const *argv[])
{
	int n;
	scanf("%d", &n);
	for(int i = 1; i < n; i++) {
		int p, q;
		scanf("%d %d", &p, &q);
		++deg[p];
		++deg[q];
		g[p].push_back(q);
		g[q].push_back(p);
	}
	int root = 0;
	for(int i = 1; i <= n; i++) {
		if(deg[i] != 1) {
			root = i;
			break;
		}
	}
	leaf(root, 0);
	dfs(root, 0);

	printf("%d\n", (nodes.size() + 1) >> 1);
	int good = nodes.front();

	while(nodes.size() > 1) {
		int p = nodes.front();
		int q = nodes.back();
		nodes.pop_front();
		nodes.pop_back();
		printf("%d %d\n", p, q);
	}
	if(!nodes.empty()) {
		printf("%d %d\n", good, nodes.front());
	}
	return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main(int, const char**)':
net.cpp:58:40: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::deque<int>::size_type {aka long unsigned int}' [-Wformat=]
  printf("%d\n", (nodes.size() + 1) >> 1);
                                        ^
net.cpp:39:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
                 ^
net.cpp:42:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &p, &q);
                         ^

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37