Submission #82584

#	Time	Username	Problem	Language	Result	Execution time	Memory
82584		bash	Network (BOI15_net)	C++17	100 / 100	538 ms	165056 KiB

net

/**
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*/
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <queue>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cassert>

#define F first
#define S second
#define endl '\n'
#define deb(x) cout<<#x<<' '<<x<<endl;
#define pb push_back

/*
#ifdef IZI_KATKA
#define int __int64_t
#else
#define int __int64
#endif
*/

const long long MOD = 1e9 + 7;
const long long MAXN = 1e6 + 1;
using namespace std;

typedef long long ll;

long long readInt() {
    bool minus1 = false;
    long long result = 0;
    char ch;
    ch = getchar();
    while (true) {
        if (ch == '-') break;
        if (ch >= '0' && ch <= '9') break;
        ch = getchar();
    }
    if (ch == '-') minus1 = true; else result = ch-'0';
    while (true) {
        ch = getchar();
        if (ch < '0' || ch > '9') break;
        result = result*10 + (ch - '0');
    }
    if (minus1)
        return -result;
    else
        return result;
}


vector <int> g[MAXN];

vector <int> ans;

void dfs(int v, int par) {
	if (g[v].size() == 1) {
		ans.pb(v);	
	}
	for (int i : g[v]) {
		if (i != par) {
			dfs(i, v);
		}
	}
}	


int main() {
	#ifdef IZI_KATKA
	assert(freopen("input", "r", stdin));
    assert(freopen("output", "w", stdout));
    #endif
    int n = readInt();
    for (int i = 1; i < n; i++) {
    	int u = readInt(), v = readInt();
    	g[u].pb(v);
    	g[v].pb(u);
    }
    dfs(1, 0);
    int sz = ans.size();
	if (sz % 2) {
		cout << sz / 2 + 1 << endl;
		for (int i = 0; i < sz / 2; i++) {
			cout << ans[i] << ' ' << ans[i + sz / 2 + 1] << endl;
		}
		cout << 1 << ' ' << ans[sz / 2] << endl;
	} else {
		cout << sz / 2 << endl;
		for (int i = 0; i < sz / 2; i++) {
			cout << ans[i] << ' ' << ans[i + sz / 2] << endl;
		}		
	}
    return 0;
}

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