Submission #901607

#	Time	Username	Problem	Language	Result	Execution time	Memory
901607		Shayan86	Mergers (JOI19_mergers)	C++17	100 / 100	831 ms	202836 KiB

mergers

#include <bits/stdc++.h>
using namespace std;

#pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// Ofast, O0, O1, O2, O3, unroll-loops, fast-math, trapv

typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;

#define Mp          make_pair
#define sep         ' '
#define endl        '\n'
#define F	        first
#define S	        second
#define pb          push_back
#define all(x)      (x).begin(),(x).end()
#define kill(res)	cout << res << '\n', exit(0);
#define set_dec(x)	cout << fixed << setprecision(x);
#define fast_io     ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io     freopen("input.txt", "r", stdin) ; freopen("output.txt", "w", stdout);

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const ll L = 22;
const ll N = 5e5 + 50;
const ll Mod = 1e9 + 7;

ll n, k, d[N], h[N], par[N][L], st[N], val[N], timer, sum[N], cnt, col[N], deg[N];

bool mark[N];
vector<int> adj[N], ost[N];

void dfs(int v, int p = 0){
    par[v][0] = p;
    for(int i = 1; i < L; i++){
        if(!par[v][i-1]) continue;
        par[v][i] = par[par[v][i-1]][i-1];
    }
    st[v] = ++timer;
    val[timer] = v;
    for(int u: adj[v]){
        if(u != p){
            h[u] = h[v] + 1;
            dfs(u, v);
        }
    }
}

int getPar(int v, int k){
    for(int i = 0; i < L; i++){
        if(k & (1 << i)) v = par[v][i];
    }
    return v;
}

int lca(int v, int u){
    if(h[v] < h[u]) swap(u, v);
    v = getPar(v, h[v] - h[u]);
    if(v == u) return v;

    for(int i = L-1; i >= 0; i--){
        if(par[v][i] != par[u][i]){
            v = par[v][i]; u = par[u][i];
        }
    }
    return par[v][0];
}

void pre(int v, int p = 0){
    for(int u: adj[v]){
        if(u == p) continue;
        pre(u, v); sum[v] += sum[u];
    }
}

void ff(int v){
    col[v] = cnt;
    mark[v] = true;
    for(int u: adj[v]){
        if(h[u] > h[v] && sum[u] == 0) continue;
        if(h[u] < h[v] && sum[v] == 0) continue;
        if(mark[u]) continue;
        ff(u);
    }
}

int main(){
    fast_io;

    cin >> n >> k;

    int u, v;
    for(int i = 1; i < n; i++){
        cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }

    for(int i = 1; i <= n; i++) cin >> d[i];

    dfs(1);

    for(int i = 1; i <= n; i++) ost[d[i]].pb(i);

    for(int i = 1; i <= k; i++){
        if(ost[i].size() <= 1) continue;
        ll mn = n+1, mx = 0;
        for(int j: ost[i]){
            mn = min(mn, st[j]); mx = max(mx, st[j]);
        }
        int top = lca(val[mn], val[mx]);

        for(int j: ost[i]){
            sum[j]++; sum[top]--;
        }
    }
    pre(1);

    for(int i = 1; i <= n; i++){
        if(!mark[i]){
            cnt++; ff(i);
        }
    }

    for(int i = 1; i <= n; i++){
        for(int j: adj[i]){
            if(h[i] < h[j] && sum[j]) continue;
            if(h[i] > h[j] && sum[i]) continue;
            deg[col[i]]++; deg[col[j]]++;
        }
    }

    ll leaf = 0;
    for(int i = 1; i <= cnt; i++) if(deg[i] == 2) leaf++;

    cout << (leaf+1)/2;

}

• Subtask 1: 10 / 10
• Subtask 2: 24 / 24
• Subtask 3: 14 / 14
• Subtask 4: 22 / 22
• Subtask 5: 30 / 30