Submission #1122895

#	Time	Username	Problem	Language	Result	Execution time	Memory
1122895		Wendidiask	Network (BOI15_net)	C++20	100 / 100	569 ms	46228 KiB

net

/*
                                     :---:--:--::::::--:-:----:                                     
                               ::-:::.                         ::-:::                               
                       .*  -===..                                    :---                           
                     .-+*##=-------====-:                                :--:                       
                  :+##=.* -=            :=+-                                .-=:                    
               .+++-.  :-   -=.            .=+-                                .--.                 
             .++=-     +      -=              :*-                                 :-.               
            +*+-      :-        -=.             -*:                                 :=:             
           #*:        *           -=.             +-                                  .=            
        =:%+         -:             -=.            +-                                   --          
        -%:          *                -=.           *:                                    +.        
       :%-..        =.                  -=.          #                                     -:       
      :=#   ..      +                     -=.        ==                                     -=      
     ---+     .    =                        -=.      .#                                      .+     
    -: ==       .  =         :------::------:.-=.     %                                       .=    
   :-  ==        .=.     ---:.               :--#+.  .%                                        :-   
   =   .*        .+.. :=-                        :++ -+                                         =:  
  +     #.       +  -=:                            :*%-*:                                        *  
 :=     :#      :=:=   .                    :-----: =+-+                                         .+ 
 *       -*     *=-     . .-        :::::::.       :*  .#+.                                       + 
:-        -+   :#.        --::-----:              :*     ++=                                      .-
+          :*. *.    .:::::*%:                   ++       +.-=.                                    +
+           -#**----:       .=                 -*.         +  -=                                   =
*           +.#=+:           +  .           .=+:           =.   -=.                                =
=            -+  :++:         +   ..     .=+=              .=     -=.                              -
=            %-     :====-:.  =.  .:--===-                  *       -=.                            -
+           +--          .:--==#==-:.=                      +         -=.                          =
*           + *                =.    :                     .=           -=.                        =
+          =  *                 +                          =              -=.                      +
:-         =  .=                =:                         =                -=.                   .-
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  *      *       :=               *                    :=                         -=             *  
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    =: -:              --:         :-           :--:                                    -=.   .=    
     =:+                  ----.     *       :---.                                         -= .+     
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    :: :=                           +:-                                                    -- :.    
        .=.                                                                               =.        
          -=                                                                            -=          
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               :--                                                                :-:               
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                       :--:                                              .--:                       
                          .-:-:                                      ::--.                          
                               :----.                          .:----                               
                                    .:::::::::-::::::--::::::::.                             
 */
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define debug(x) cerr << #x << " is " << x << "\n"
#define hehe ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define rep(i, a, b) for (int i = a; i <= b; i++)
#define repb(i, a, b) for (int i = b; i >= a; i--)
#define pii pair<int, int>
#define linebreak cout << "---------------------------------------------------------\n"
#define f first
#define s second
#define pb push_back
// good luck
const int MS = 5e5+5, mod = 1e9+7;
int n;
vector<int> adj[MS], v;
void dfs(int x, int par) {
	if (adj[x].size() == 1) v.pb(x);
	for (auto v : adj[x]) {
		if (v == par) continue;
		dfs(v, x);
	}
}
int32_t main() {
	cin >> n;
	for (int i = 0; i < n-1; i++) {
		int a, b; cin >> a >> b;
		adj[a].pb(b);
		adj[b].pb(a);
	}
	dfs(1, -1);
	cout << (v.size()+1)/2 << '\n';
	for (int i = 0; i < v.size()/2; i++) cout << v[i] << " " << v[i+v.size()/2] << '\n';
	if (v.size()%2 == 1) cout << v[v.size()-1] << " " << v[0];
}

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