Submission #342373

#	Time	Username	Problem	Language	Result	Execution time	Memory
342373		limabeans	Papričice (COCI20_papricice)	C++17	50 / 110	1097 ms	29292 KiB

papricice

#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;

set<int> A, B;

void dfs(int at, int p) {
    for (int y: A) {
	lo = min(lo, get({siz[at],siz[y]-siz[at],n-siz[y]}));
    }
    for (int y: B) {
	lo = min(lo, get({siz[at],siz[y],n-siz[at]-siz[y]}));
    }
    
    A.insert(at);
    for (int to: g[at]) {
	if (to == p) continue;
	dfs(to, at);
    }
    A.erase(at);
    B.insert(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: 15 / 15
• Subtask 2: 35 / 35
• Subtask 3: 0 / 60