Submission #120012

#	Time	Username	Problem	Language	Result	Execution time	Memory
120012		E869120	Network (BOI15_net)	C++14	100 / 100	951 ms	54892 KiB

net

#include <iostream>
#include <vector>
using namespace std;
#pragma warning (disable: 4996)

int N, A[1 << 19], B[1 << 19]; bool used[1 << 19];
vector<int> G[1 << 19], I;

void dfs(int pos) {
	if (used[pos] == true) return;
	used[pos] = true;
	if (G[pos].size() == 1) I.push_back(pos);
	for (int i = 0; i < G[pos].size(); i++) dfs(G[pos][i]);
}

int main() {
	scanf("%d", &N);
	for (int i = 1; i <= N - 1; i++) {
		scanf("%d%d", &A[i], &B[i]);
		G[A[i]].push_back(B[i]);
		G[B[i]].push_back(A[i]);
	}
	int root = -1;
	for (int i = 1; i <= N; i++) {
		if (G[i].size() >= 2) root = i;
	}
	dfs(root);
	int mid = I.size() / 2;
	cout << I.size() - mid << endl;
	for (int i = 0; i < I.size() - mid; i++) cout << I[i] << " " << I[i + mid] << endl;
	return 0;
}

Compilation message (stderr)

net.cpp:4:0: warning: ignoring #pragma warning  [-Wunknown-pragmas]
 #pragma warning (disable: 4996)
 
net.cpp: In function 'void dfs(int)':
net.cpp:13:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < G[pos].size(); i++) dfs(G[pos][i]);
                  ~~^~~~~~~~~~~~~~~
net.cpp: In function 'int main()':
net.cpp:30:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < I.size() - mid; i++) cout << I[i] << " " << I[i + mid] << endl;
                  ~~^~~~~~~~~~~~~~~~
net.cpp:17:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &N);
  ~~~~~^~~~~~~~~~
net.cpp:19:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &A[i], &B[i]);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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