oj.uz

답안 #342376

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
342376 2021-01-02T02:46:44 Z limabeans Papričice (COCI20_papricice) C++17
0 / 110
 4 ms 5248 KB 
#include <bits/stdc++.h>
using namespace std;

template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl







const int maxn = 2e5 + 10;
const int LOG = 20;

int n;
vector<int> g[maxn];
int par[LOG+1][maxn];
int dep[maxn];
int siz[maxn];

void hack(int at, int p=0) {
    for (int i=1; i<LOG; i++) {
	par[i][at] = par[i-1][par[i-1][at]];
    }

    siz[at] = 1;
    
    for (int to: g[at]) {
	if (to==p) continue;
	dep[to]=1+dep[at];
	par[0][to]=at;
	hack(to, at);
	siz[at] += siz[to];
    }
}


int lca(int u, int v) {
    if (dep[u] < dep[v]) swap(u,v);
    int dx = dep[u]-dep[v];
    for (int i=0; i<LOG; i++) {
	if (dx>>i&1) {
	    u = par[i][u];
	}
    }
    if (u==v) return u;

    for (int j=LOG-1; j>=0; j--) {
	if (par[j][u]!=par[j][v]) {
	    u = par[j][u];
	    v = par[j][v];
	}
    }

    return par[0][u];
}

int get(vector<int> a) {
    sort(a.begin(),a.end());
    return a[2]-a[0];
}

int lo;


vector<int> vfind(multiset<int> &s, int x) {
    if (s.empty()) return {};
    
    auto iter = s.lower_bound(x);
    if (iter == s.end()) --iter;


    vector<int> res;
    res.push_back(*iter);
    auto piter = iter;
    
    //fwd
    for (int it=0; it<2; it++) {
	++iter;
	if (iter==s.end()) break;
	res.push_back(*iter);	
    }

    iter = piter;
    //prv
    for (int it=0; it<2; it++) {
	if (iter==s.begin()) break;
	--iter;
	res.push_back(*iter);	
    }
    
    return res;
}

multiset<int> A, B;

vector<int> solveA(int x) {
    vector<int> res;
    
    auto tmp = vfind(A, (n+x)/2);
    res.insert(res.end(), tmp.begin(), tmp.end());
    tmp = vfind(A, (n+x+1)/2);
    res.insert(res.end(), tmp.begin(), tmp.end());

    tmp = vfind(A, n-x);
    res.insert(res.end(), tmp.begin(), tmp.end());

    tmp = vfind(A, 2*x);
    res.insert(res.end(), tmp.begin(), tmp.end());
    
    return res;
}

vector<int> solveB(int x) {
    vector<int> res;

    auto tmp = vfind(A, (n-x)/2);
    res.insert(res.end(), tmp.begin(), tmp.end());
    tmp = vfind(A, (n-x+1)/2);
    res.insert(res.end(), tmp.begin(), tmp.end());

    tmp = vfind(A, x);
    res.insert(res.end(), tmp.begin(), tmp.end());

    tmp = vfind(A, n-2*x);
    res.insert(res.end(), tmp.begin(), tmp.end());


    return res;
}

void dfs(int at, int p) {
    for (int ysiz: solveA(siz[at])) {
	int cur = get({siz[at], ysiz-siz[at], n-ysiz});
	lo = min(lo, cur);
    }

    for (int ysiz: solveB(siz[at])) {
	int cur = get({siz[at], ysiz, n-siz[at]-ysiz});
	lo = min(lo, cur);	
    }
    
    A.insert(siz[at]);
    
    for (int to: g[at]) {
	if (to == p) continue;
	dfs(to, at);
    }
    
    A.erase(A.find(siz[at]));
    B.insert(siz[at]);
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);  cout.tie(0);

    cin>>n;
    for (int i=0; i<n-1; i++) {
	int u,v; cin>>u>>v;
	g[u].push_back(v);
	g[v].push_back(u);
    }

    assert(n>=3);
    hack(1);

    lo = n;
    dfs(1,0);


    cout<<lo<<endl;    
    return 0;
}

Subtask #1
0 / 15.0

# 결과 실행 시간 메모리 Grader output
1 Correct 4 ms 5228 KB Output is correct
2 Correct 4 ms 5248 KB Output is correct
3 Incorrect 4 ms 5228 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #2
0 / 35.0

# 결과 실행 시간 메모리 Grader output
1 Correct 4 ms 5228 KB Output is correct
2 Correct 4 ms 5248 KB Output is correct
3 Incorrect 4 ms 5228 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #3
0 / 60.0

# 결과 실행 시간 메모리 Grader output
1 Correct 4 ms 5228 KB Output is correct
2 Correct 4 ms 5248 KB Output is correct
3 Incorrect 4 ms 5228 KB Output isn't correct
4 Halted 0 ms 0 KB -