Submission #148102

#	Time	Username	Problem	Language	Result	Execution time	Memory
148102		WhipppedCream	Network (BOI15_net)	C++17	100 / 100	585 ms	57848 KiB

net

#include <bits/stdc++.h>
//#ifdef atom #else #endif
using namespace std;
typedef long long ll; typedef pair<int, int> ii;
#define X first
#define Y second
#define vi vector<int>
#define vii vector< ii >
#define pb push_back
const int maxn = 5e5+5;
vi adj[maxn];
vi leaf;
void dfs(int u, int p)
{
    bool found = 0;
    for(auto v : adj[u])
    {
        if(v == p) continue;
        dfs(v, u);
        found = 1;
    }
    if(!found) leaf.pb(u);
}
int main()
{
    //#ifndef atom freopen(".in", "r", stdin); freopen(".out", "w", stdout); #endif
    int n; scanf("%d", &n);
    for(int i = 0; i< n-1; i++)
    {
        int u, v; scanf("%d %d", &u, &v);
        adj[u].pb(v); adj[v].pb(u);
    }
    int s = 1;
    for(int i = 1; i<= n; i++) if(adj[i].size()> 1) s = i;
    dfs(s, 0);
    printf("%d\n", (leaf.size()+1)/2);
    int mid = (leaf.size()+1)/2;
    for(int i = 0; i< mid; i++)
    {
        printf("%d %d\n", leaf[i], leaf[min((int) leaf.size()-1, mid+i)]);
    }
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:36:37: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type {aka long unsigned int}' [-Wformat=]
     printf("%d\n", (leaf.size()+1)/2);
                    ~~~~~~~~~~~~~~~~~^
net.cpp:27:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     int n; scanf("%d", &n);
            ~~~~~^~~~~~~~~~
net.cpp:30:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int u, v; scanf("%d %d", &u, &v);
                   ~~~~~^~~~~~~~~~~~~~~~~

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