// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
- insert(x),erase(x)
- find_by_order(k): return iterator to the k-th smallest element
- order_of_key(x): the number of elements that are strictly smaller
*/
#include<bits/stdc++.h>
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
uniform_real_distribution<> pp(0.0,1.0);
//#define int long long
#define ld long double
#define pii pair<int,int>
#define piii pair<int,pii>
#define mpp make_pair
#define fi first
#define se second
//const int inf=1e18;
const int mod=998244353;
const int maxn=500005;
const int bl=650;
const int maxs=655;
const int maxm=200005;
const int maxq=1000005;
const int maxl=20;
const int maxa=1000000;
const int root=3;
/*
int power(int a,int n){
int res=1;
while(n){
if(n&1) res=res*a%mod;
a=a*a%mod;n>>=1;
}
return res;
}
const int iroot=power(3,mod-2);
*/
const int base=101;
pii p[maxn];
vector<pii> ans;
vector<int> edge[maxn];
void dfs(int u,int par){
if((int)edge[u].size()==1){
p[u]={-1,u};
return;
}
deque<int> f1;
pii f2={-1,-1};
for(int v:edge[u]){
if(v==par) continue;
dfs(v,u);
if(p[v].fi==-1) f1.push_back(p[v].se);
else if(f2.fi==-1) f2=p[v];
else{
ans.push_back({f2.se,p[v].fi});
f2.se=p[v].se;
}
}
if(f2.fi!=-1){
f1.push_front(f2.fi);
f1.push_back(f2.se);
}
while((int)f1.size()>=3){
int x=f1.back();f1.pop_back();
int y=f1.back();f1.pop_back();
ans.push_back({x,y});
}
if((int)f1.size()>=2) p[u]={f1[0],f1[1]};
else p[u]={-1,f1[0]};
}
void solve(){
int n;cin >> n;
for(int i=1;i<n;i++){
int u,v;cin >> u >> v;
edge[u].push_back(v);
edge[v].push_back(u);
}
int rt=1;
while((int)edge[rt].size()==1) rt++;
dfs(rt,0);
if(p[rt].fi==-1) ans.push_back({rt,p[rt].se});
else ans.push_back(p[rt]);
cout << (int)ans.size() << '\n';
for(auto &[x,y]:ans) cout << x << ' ' << y << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
int test=1;//cin >> test;
while(test--) solve();
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
7 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
11988 KB |
Output is correct |
3 |
Correct |
6 ms |
12000 KB |
Output is correct |
4 |
Correct |
5 ms |
12076 KB |
Output is correct |
5 |
Correct |
5 ms |
11988 KB |
Output is correct |
6 |
Correct |
5 ms |
12076 KB |
Output is correct |
7 |
Correct |
5 ms |
11988 KB |
Output is correct |
8 |
Correct |
6 ms |
12076 KB |
Output is correct |
9 |
Correct |
7 ms |
12072 KB |
Output is correct |
10 |
Correct |
6 ms |
12076 KB |
Output is correct |
11 |
Correct |
7 ms |
12068 KB |
Output is correct |
12 |
Correct |
6 ms |
12052 KB |
Output is correct |
13 |
Correct |
7 ms |
12072 KB |
Output is correct |
14 |
Correct |
7 ms |
12008 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
6 ms |
11988 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
12072 KB |
Output is correct |
20 |
Correct |
5 ms |
11988 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
7 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
11988 KB |
Output is correct |
3 |
Correct |
6 ms |
12000 KB |
Output is correct |
4 |
Correct |
5 ms |
12076 KB |
Output is correct |
5 |
Correct |
5 ms |
11988 KB |
Output is correct |
6 |
Correct |
5 ms |
12076 KB |
Output is correct |
7 |
Correct |
5 ms |
11988 KB |
Output is correct |
8 |
Correct |
6 ms |
12076 KB |
Output is correct |
9 |
Correct |
7 ms |
12072 KB |
Output is correct |
10 |
Correct |
6 ms |
12076 KB |
Output is correct |
11 |
Correct |
7 ms |
12068 KB |
Output is correct |
12 |
Correct |
6 ms |
12052 KB |
Output is correct |
13 |
Correct |
7 ms |
12072 KB |
Output is correct |
14 |
Correct |
7 ms |
12008 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
6 ms |
11988 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
12072 KB |
Output is correct |
20 |
Correct |
5 ms |
11988 KB |
Output is correct |
21 |
Correct |
6 ms |
12072 KB |
Output is correct |
22 |
Correct |
6 ms |
12116 KB |
Output is correct |
23 |
Correct |
6 ms |
12100 KB |
Output is correct |
24 |
Correct |
9 ms |
12244 KB |
Output is correct |
25 |
Correct |
6 ms |
12176 KB |
Output is correct |
26 |
Correct |
6 ms |
12116 KB |
Output is correct |
27 |
Correct |
8 ms |
12084 KB |
Output is correct |
28 |
Correct |
6 ms |
12092 KB |
Output is correct |
29 |
Correct |
6 ms |
12092 KB |
Output is correct |
30 |
Correct |
6 ms |
11988 KB |
Output is correct |
31 |
Correct |
8 ms |
12088 KB |
Output is correct |
32 |
Correct |
6 ms |
12080 KB |
Output is correct |
33 |
Correct |
6 ms |
11988 KB |
Output is correct |
34 |
Correct |
6 ms |
11988 KB |
Output is correct |
35 |
Correct |
6 ms |
12080 KB |
Output is correct |
36 |
Correct |
6 ms |
12084 KB |
Output is correct |
37 |
Correct |
7 ms |
12300 KB |
Output is correct |
38 |
Correct |
7 ms |
12628 KB |
Output is correct |
39 |
Correct |
6 ms |
12072 KB |
Output is correct |
40 |
Correct |
6 ms |
12076 KB |
Output is correct |
41 |
Correct |
6 ms |
11988 KB |
Output is correct |
42 |
Correct |
6 ms |
12104 KB |
Output is correct |
43 |
Correct |
6 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11988 KB |
Output is correct |
45 |
Correct |
6 ms |
11988 KB |
Output is correct |
46 |
Correct |
6 ms |
12116 KB |
Output is correct |
47 |
Correct |
6 ms |
12076 KB |
Output is correct |
48 |
Correct |
6 ms |
11988 KB |
Output is correct |
49 |
Correct |
6 ms |
12084 KB |
Output is correct |
50 |
Correct |
5 ms |
11988 KB |
Output is correct |
51 |
Correct |
6 ms |
12072 KB |
Output is correct |
52 |
Correct |
6 ms |
12116 KB |
Output is correct |
53 |
Correct |
6 ms |
12208 KB |
Output is correct |
54 |
Correct |
6 ms |
12072 KB |
Output is correct |
55 |
Correct |
6 ms |
11988 KB |
Output is correct |
56 |
Correct |
5 ms |
11988 KB |
Output is correct |
57 |
Correct |
6 ms |
12068 KB |
Output is correct |
58 |
Correct |
8 ms |
12112 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
7 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
11988 KB |
Output is correct |
3 |
Correct |
6 ms |
12000 KB |
Output is correct |
4 |
Correct |
5 ms |
12076 KB |
Output is correct |
5 |
Correct |
5 ms |
11988 KB |
Output is correct |
6 |
Correct |
5 ms |
12076 KB |
Output is correct |
7 |
Correct |
5 ms |
11988 KB |
Output is correct |
8 |
Correct |
6 ms |
12076 KB |
Output is correct |
9 |
Correct |
7 ms |
12072 KB |
Output is correct |
10 |
Correct |
6 ms |
12076 KB |
Output is correct |
11 |
Correct |
7 ms |
12068 KB |
Output is correct |
12 |
Correct |
6 ms |
12052 KB |
Output is correct |
13 |
Correct |
7 ms |
12072 KB |
Output is correct |
14 |
Correct |
7 ms |
12008 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
6 ms |
11988 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
12072 KB |
Output is correct |
20 |
Correct |
5 ms |
11988 KB |
Output is correct |
21 |
Correct |
6 ms |
12072 KB |
Output is correct |
22 |
Correct |
6 ms |
12116 KB |
Output is correct |
23 |
Correct |
6 ms |
12100 KB |
Output is correct |
24 |
Correct |
9 ms |
12244 KB |
Output is correct |
25 |
Correct |
6 ms |
12176 KB |
Output is correct |
26 |
Correct |
6 ms |
12116 KB |
Output is correct |
27 |
Correct |
8 ms |
12084 KB |
Output is correct |
28 |
Correct |
6 ms |
12092 KB |
Output is correct |
29 |
Correct |
6 ms |
12092 KB |
Output is correct |
30 |
Correct |
6 ms |
11988 KB |
Output is correct |
31 |
Correct |
8 ms |
12088 KB |
Output is correct |
32 |
Correct |
6 ms |
12080 KB |
Output is correct |
33 |
Correct |
6 ms |
11988 KB |
Output is correct |
34 |
Correct |
6 ms |
11988 KB |
Output is correct |
35 |
Correct |
6 ms |
12080 KB |
Output is correct |
36 |
Correct |
6 ms |
12084 KB |
Output is correct |
37 |
Correct |
7 ms |
12300 KB |
Output is correct |
38 |
Correct |
7 ms |
12628 KB |
Output is correct |
39 |
Correct |
6 ms |
12072 KB |
Output is correct |
40 |
Correct |
6 ms |
12076 KB |
Output is correct |
41 |
Correct |
6 ms |
11988 KB |
Output is correct |
42 |
Correct |
6 ms |
12104 KB |
Output is correct |
43 |
Correct |
6 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11988 KB |
Output is correct |
45 |
Correct |
6 ms |
11988 KB |
Output is correct |
46 |
Correct |
6 ms |
12116 KB |
Output is correct |
47 |
Correct |
6 ms |
12076 KB |
Output is correct |
48 |
Correct |
6 ms |
11988 KB |
Output is correct |
49 |
Correct |
6 ms |
12084 KB |
Output is correct |
50 |
Correct |
5 ms |
11988 KB |
Output is correct |
51 |
Correct |
6 ms |
12072 KB |
Output is correct |
52 |
Correct |
6 ms |
12116 KB |
Output is correct |
53 |
Correct |
6 ms |
12208 KB |
Output is correct |
54 |
Correct |
6 ms |
12072 KB |
Output is correct |
55 |
Correct |
6 ms |
11988 KB |
Output is correct |
56 |
Correct |
5 ms |
11988 KB |
Output is correct |
57 |
Correct |
6 ms |
12068 KB |
Output is correct |
58 |
Correct |
8 ms |
12112 KB |
Output is correct |
59 |
Correct |
291 ms |
39488 KB |
Output is correct |
60 |
Correct |
318 ms |
42624 KB |
Output is correct |
61 |
Correct |
6 ms |
12072 KB |
Output is correct |
62 |
Correct |
7 ms |
12052 KB |
Output is correct |
63 |
Correct |
206 ms |
37048 KB |
Output is correct |
64 |
Correct |
9 ms |
16084 KB |
Output is correct |
65 |
Correct |
21 ms |
27356 KB |
Output is correct |
66 |
Correct |
189 ms |
154252 KB |
Output is correct |
67 |
Correct |
546 ms |
248048 KB |
Output is correct |
68 |
Correct |
563 ms |
252288 KB |
Output is correct |
69 |
Correct |
10 ms |
13072 KB |
Output is correct |
70 |
Correct |
56 ms |
23136 KB |
Output is correct |
71 |
Correct |
213 ms |
47884 KB |
Output is correct |
72 |
Correct |
216 ms |
46504 KB |
Output is correct |
73 |
Correct |
55 ms |
20180 KB |
Output is correct |
74 |
Correct |
311 ms |
41596 KB |
Output is correct |
75 |
Correct |
21 ms |
15812 KB |
Output is correct |
76 |
Correct |
195 ms |
47156 KB |
Output is correct |
77 |
Correct |
198 ms |
47060 KB |
Output is correct |
78 |
Correct |
34 ms |
30696 KB |
Output is correct |
79 |
Correct |
545 ms |
218952 KB |
Output is correct |
80 |
Correct |
7 ms |
12372 KB |
Output is correct |
81 |
Correct |
65 ms |
22632 KB |
Output is correct |
82 |
Correct |
270 ms |
44884 KB |
Output is correct |
83 |
Correct |
322 ms |
41496 KB |
Output is correct |
84 |
Correct |
337 ms |
41580 KB |
Output is correct |
85 |
Correct |
378 ms |
41548 KB |
Output is correct |
86 |
Correct |
295 ms |
42632 KB |
Output is correct |
87 |
Correct |
304 ms |
42688 KB |
Output is correct |