oj.uz

Submission #321159

# Submission time Handle Problem Language Result Execution time Memory
321159 2020-11-11T08:55:15 Z AmineWeslati Network (BOI15_net) C++14
63 / 100
 162 ms 9964 KB 
//Never stop trying
/*#pragma GCC target ("avx2")
#pragma GCC optimize ("Ofast")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")*/
#include "bits/stdc++.h"
using namespace std;
#define boost ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)

typedef long long ll;
#define int ll
typedef string str;
typedef double db;
typedef long double ld;
typedef pair<int, int> pi;
#define fi first
#define se second
typedef vector<int> vi;
typedef vector<pi> vpi;
typedef vector<str> vs;
typedef vector<ld> vd;
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define endl "\n"

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)

const int MOD = 1e9 + 7; //998244353
const ll INF = 1e18;
const int MX = 2e5 + 10;
const int nx[4] = {0, 0, 1, -1}, ny[4] = {1, -1, 0, 0}; //right left down up

template<class T> using V = vector<T>;
template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }

ll cdiv(ll a, ll b) { return a / b + ((a ^ b) > 0 && a % b); } // divide a by b rounded up
//constexpr int log2(int x) { return 31 - __builtin_clz(x); } // floor(log2(x))

mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
//mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());

ll random(ll a, ll b){
    return a + rng() % (b - a + 1);
}

#ifndef LOCAL  
#define cerr if(false) cerr
#endif
#define dbg(x) cerr << #x << " : " << x << endl; 
#define dbgs(x,y) cerr << #x << " : " << x << " / " << #y << " : " << y << endl;
#define dbgv(v) cerr << #v << " : " << "[ "; for(auto it : v) cerr << it << ' '; cerr << ']' << endl;
#define here() cerr << "here" << endl;

void IO() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
}

int N; 
vpi adj[MX];

bool finished(){
	FOR(u,1,N+1) for(auto ed: adj[u]) if(ed.se==1) return 0;
	return 1; 
}

int val[MX],mxVal[MX],parent[MX];
void dfs(int u, int p){
	parent[u]=p;
	val[u]=0,mxVal[u]=0;
	vi vec;
	for(auto v: adj[u]) if(v.fi!=p){
		dfs(v.fi,u);
		int x=mxVal[v.fi]+v.se;
		vec.pb(x);
		ckmax(mxVal[u],x);
	}

	sort(rall(vec));
	if(sz(vec)) val[u]=vec[0];
	if(sz(vec)>1) val[u]+=vec[1];
}

int32_t main() {
    boost; IO();

    cin>>N;
    FOR(i,0,N-1){
    	int u,v; cin>>u>>v;
    	adj[u].pb({v,1});
    	adj[v].pb({u,1});
    }

    vpi res;
    while(!finished()){
    	dfs(1,1);
    	int mx=-1,u;
    	FOR(i,1,N+1) if(ckmax(mx,val[i])) u=i;
    	//dbgs(u,val[u]);
    	//cout << val[4] << endl;

    	int a=u,b=u,pa=parent[u],pb=parent[u];
    	bool taken[N+1]; fill(taken,taken+N+1,0);

    	while(sz(adj[a])>1 || a==1){
    		int mx=-1,nxt;
    		for(auto v: adj[a]) 
    			if(v.fi!=pa && ckmax(mx,mxVal[v.fi]+v.se)) 
    				nxt=v.fi;

    		for(auto &v: adj[a]) if(v.fi==nxt) v.se=0;
    		for(auto &v: adj[nxt]) if(v.fi==a) v.se=0;
    		taken[nxt]=true;
    		pa=a; a=nxt; 
    	}

    	dfs(1,1);

    	while(sz(adj[b])>1 || b==1){
    		int mx=-1,nxt;
    		for(auto v: adj[b]) 
    			if(v.fi!=pb && !taken[v.fi] && ckmax(mx,mxVal[v.fi]+v.se)) 
    				nxt=v.fi;
			if(mx==-1) break;
    		for(auto &v: adj[b]) if(v.fi==nxt) v.se=0;
    		for(auto &v: adj[nxt]) if(v.fi==b) v.se=0;
    		pb=b; b=nxt; 
    	}
    	dbg(u);
    	dbgs(a,b);
    	assert(a!=b);
    	res.pb({a,b});
    }
    cout << sz(res) << endl;
    for(auto x: res) cout << x.fi << ' ' << x.se << endl;
    

    return 0;
}

/* Careful!!!
    .Array bounds
    .Infinite loops
    .Uninitialized variables / empty containers
    .Multisets are shit

   Some insights:
    .Binary search
    .Graph representation
    .Write brute force code
    .Change your approach
*/

Compilation message

net.cpp: In function 'int32_t main()':
net.cpp:128:7: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  128 |       for(auto v: adj[b])
      |       ^~~
net.cpp:131:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  131 |    if(mx==-1) break;
      |    ^~
net.cpp:118:28: warning: 'nxt' may be used uninitialized in this function [-Wmaybe-uninitialized]
  118 |       for(auto &v: adj[a]) if(v.fi==nxt) v.se=0;
      |                            ^~
net.cpp:112:25: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
  112 |      while(sz(adj[a])>1 || a==1){
      |                         ^

Subtask #1
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5100 KB Output is correct
2 Correct 4 ms 5100 KB Output is correct
3 Correct 4 ms 5100 KB Output is correct
4 Correct 4 ms 5100 KB Output is correct
5 Correct 4 ms 5100 KB Output is correct
6 Correct 4 ms 5100 KB Output is correct
7 Correct 4 ms 5120 KB Output is correct
8 Correct 4 ms 5100 KB Output is correct
9 Correct 4 ms 5100 KB Output is correct
10 Correct 4 ms 5100 KB Output is correct
11 Correct 4 ms 5100 KB Output is correct
12 Correct 4 ms 5120 KB Output is correct
13 Correct 4 ms 5100 KB Output is correct
14 Correct 4 ms 5120 KB Output is correct
15 Correct 3 ms 5100 KB Output is correct
16 Correct 4 ms 5100 KB Output is correct
17 Correct 4 ms 5100 KB Output is correct
18 Correct 4 ms 5100 KB Output is correct
19 Correct 4 ms 5100 KB Output is correct
20 Correct 4 ms 5100 KB Output is correct

Subtask #2
45.0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5100 KB Output is correct
2 Correct 4 ms 5100 KB Output is correct
3 Correct 4 ms 5100 KB Output is correct
4 Correct 4 ms 5100 KB Output is correct
5 Correct 4 ms 5100 KB Output is correct
6 Correct 4 ms 5100 KB Output is correct
7 Correct 4 ms 5120 KB Output is correct
8 Correct 4 ms 5100 KB Output is correct
9 Correct 4 ms 5100 KB Output is correct
10 Correct 4 ms 5100 KB Output is correct
11 Correct 4 ms 5100 KB Output is correct
12 Correct 4 ms 5120 KB Output is correct
13 Correct 4 ms 5100 KB Output is correct
14 Correct 4 ms 5120 KB Output is correct
15 Correct 3 ms 5100 KB Output is correct
16 Correct 4 ms 5100 KB Output is correct
17 Correct 4 ms 5100 KB Output is correct
18 Correct 4 ms 5100 KB Output is correct
19 Correct 4 ms 5100 KB Output is correct
20 Correct 4 ms 5100 KB Output is correct
21 Correct 4 ms 5100 KB Output is correct
22 Correct 105 ms 5228 KB Output is correct
23 Correct 92 ms 5228 KB Output is correct
24 Correct 103 ms 5348 KB Output is correct
25 Correct 110 ms 5228 KB Output is correct
26 Correct 57 ms 5228 KB Output is correct
27 Correct 162 ms 5348 KB Output is correct
28 Correct 143 ms 5228 KB Output is correct
29 Correct 91 ms 5228 KB Output is correct
30 Correct 4 ms 5100 KB Output is correct
31 Correct 159 ms 5420 KB Output is correct
32 Correct 4 ms 5100 KB Output is correct
33 Correct 4 ms 5100 KB Output is correct
34 Correct 4 ms 5100 KB Output is correct
35 Correct 4 ms 5100 KB Output is correct
36 Correct 4 ms 5100 KB Output is correct
37 Correct 5 ms 5228 KB Output is correct
38 Correct 7 ms 5228 KB Output is correct
39 Correct 4 ms 5100 KB Output is correct
40 Correct 4 ms 5100 KB Output is correct
41 Correct 4 ms 5100 KB Output is correct
42 Correct 10 ms 5100 KB Output is correct
43 Correct 30 ms 5220 KB Output is correct
44 Correct 4 ms 5248 KB Output is correct
45 Correct 9 ms 5100 KB Output is correct
46 Correct 36 ms 5228 KB Output is correct
47 Correct 4 ms 5248 KB Output is correct
48 Correct 6 ms 5100 KB Output is correct
49 Correct 32 ms 5220 KB Output is correct
50 Correct 4 ms 5100 KB Output is correct
51 Correct 4 ms 5100 KB Output is correct
52 Correct 5 ms 5100 KB Output is correct
53 Correct 26 ms 5228 KB Output is correct
54 Correct 4 ms 5100 KB Output is correct
55 Correct 13 ms 5100 KB Output is correct
56 Correct 4 ms 5100 KB Output is correct
57 Correct 10 ms 5100 KB Output is correct
58 Correct 105 ms 5348 KB Output is correct

Subtask #3
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5100 KB Output is correct
2 Correct 4 ms 5100 KB Output is correct
3 Correct 4 ms 5100 KB Output is correct
4 Correct 4 ms 5100 KB Output is correct
5 Correct 4 ms 5100 KB Output is correct
6 Correct 4 ms 5100 KB Output is correct
7 Correct 4 ms 5120 KB Output is correct
8 Correct 4 ms 5100 KB Output is correct
9 Correct 4 ms 5100 KB Output is correct
10 Correct 4 ms 5100 KB Output is correct
11 Correct 4 ms 5100 KB Output is correct
12 Correct 4 ms 5120 KB Output is correct
13 Correct 4 ms 5100 KB Output is correct
14 Correct 4 ms 5120 KB Output is correct
15 Correct 3 ms 5100 KB Output is correct
16 Correct 4 ms 5100 KB Output is correct
17 Correct 4 ms 5100 KB Output is correct
18 Correct 4 ms 5100 KB Output is correct
19 Correct 4 ms 5100 KB Output is correct
20 Correct 4 ms 5100 KB Output is correct
21 Correct 4 ms 5100 KB Output is correct
22 Correct 105 ms 5228 KB Output is correct
23 Correct 92 ms 5228 KB Output is correct
24 Correct 103 ms 5348 KB Output is correct
25 Correct 110 ms 5228 KB Output is correct
26 Correct 57 ms 5228 KB Output is correct
27 Correct 162 ms 5348 KB Output is correct
28 Correct 143 ms 5228 KB Output is correct
29 Correct 91 ms 5228 KB Output is correct
30 Correct 4 ms 5100 KB Output is correct
31 Correct 159 ms 5420 KB Output is correct
32 Correct 4 ms 5100 KB Output is correct
33 Correct 4 ms 5100 KB Output is correct
34 Correct 4 ms 5100 KB Output is correct
35 Correct 4 ms 5100 KB Output is correct
36 Correct 4 ms 5100 KB Output is correct
37 Correct 5 ms 5228 KB Output is correct
38 Correct 7 ms 5228 KB Output is correct
39 Correct 4 ms 5100 KB Output is correct
40 Correct 4 ms 5100 KB Output is correct
41 Correct 4 ms 5100 KB Output is correct
42 Correct 10 ms 5100 KB Output is correct
43 Correct 30 ms 5220 KB Output is correct
44 Correct 4 ms 5248 KB Output is correct
45 Correct 9 ms 5100 KB Output is correct
46 Correct 36 ms 5228 KB Output is correct
47 Correct 4 ms 5248 KB Output is correct
48 Correct 6 ms 5100 KB Output is correct
49 Correct 32 ms 5220 KB Output is correct
50 Correct 4 ms 5100 KB Output is correct
51 Correct 4 ms 5100 KB Output is correct
52 Correct 5 ms 5100 KB Output is correct
53 Correct 26 ms 5228 KB Output is correct
54 Correct 4 ms 5100 KB Output is correct
55 Correct 13 ms 5100 KB Output is correct
56 Correct 4 ms 5100 KB Output is correct
57 Correct 10 ms 5100 KB Output is correct
58 Correct 105 ms 5348 KB Output is correct
59 Runtime error 10 ms 9964 KB Execution killed with signal 11 (could be triggered by violating memory limits)
60 Halted 0 ms 0 KB -