Submission #944605

#	Time	Username	Problem	Language	Result	Execution time	Memory
944605		VinhLuu	Mergers (JOI19_mergers)	C++17	100 / 100	1275 ms	182712 KiB

mergers

//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#include <bits/stdc++.h>
//#define int long long
#define ll long long
#define fi first
#define se second
#define pb push_back
#define all(lmao) lmao.begin(), lmao.end()

using namespace std;

typedef pair<int,int> pii;
typedef tuple<int,int,int> tp;
const int N = 5e5 + 5;
const ll oo = 1e16;
const int mod = 1e9 + 7;
const int base = 23;

int n, pa[N], sz[N], g[N], k, ans, X[N], Y[N], col[N], a[N], f[N][22], dp[N], in[N], en[N], demin, b[N], st[N << 1];
vector<int> p[N], vr[N], open[N];
bool fl[N];

int fin(int u){
    return pa[u] == u ? u :  pa[u] = fin(pa[u]);
}

void dsu(int u,int v){
    u = fin(u);
    v = fin(v);
    if(u == v) return;
    if(sz[u] < sz[v]) swap(u, v);
    sz[u] += sz[v];
    pa[v] = u;
}

void update(int i){
    i += n - 1;
    st[i] ++;
    while(i > 1){
        i /= 2;
        st[i]++;
    }
}

int get(int l,int r){
    r++;
    int ret = 0;
    for(l += n - 1, r += n - 1; l < r; l /= 2, r /= 2){
        if(l & 1) ret += st[l ++];
        if(r & 1) ret += st[-- r];
    }
    return ret;
}

void pre(int u,int v){
    dp[u] = ((int)p[u].size() == 1);
    if(v == 0) for(int i = 0; i <= 20; i ++) f[u][i] = u;
    else{
        f[u][0] = v;
        for(int i = 1; i <= 20; i ++) f[u][i] = f[f[u][i - 1]][i - 1];
    }
    in[u] = ++demin;
    b[demin] = u;
    for(auto j : p[u]){
        if(j == v) continue;
        pre(j, u);
        dp[u] += dp[j];
    }
    en[u] = demin;
}

bool kt(int u,int v){
    return in[u] <= in[v] && en[u] >= in[v];
}

int lca(int u,int v){
    int kq = u;
    if(kt(u, v)) return u;
    else{
        for(int i = 20; i >= 0; i --){
            if(kt(f[u][i], v)) kq = f[u][i];
            else u = f[u][i];
        }
        return kq;
    }
}

void dfs(int u,int v){
    for(auto j : p[u]){
        if(j == v) continue;
        dfs(j, u);
    }
    for(auto j : open[u]){
        for(auto o : vr[j]) update(in[o]);
    }
    if(v && get(in[u], en[u]) != (en[u] - in[u] + 1)){
        dsu(u, v);
    }
}

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

    #define task "v"
    if(fopen(task ".inp","r")){
        freopen(task ".inp","r",stdin);
        freopen(task ".out","w",stdout);
    }

    cin >> n >> k;

    for(int i = 1; i <= n - 1; i ++){
        cin >> X[i] >> Y[i];
        p[X[i]].pb(Y[i]);
        p[Y[i]].pb(X[i]);
    }
    int root = 1, tmp = 1;
    for(int i = 1; i <= n; i ++){
        pa[i] = i, sz[i] = 1;
        if((int)p[i].size() > tmp) root = i, tmp = (int)p[i].size();
        int x; cin >> x;
        vr[x].pb(i);
        col[i] = x;
    }
    if(n == 1){
        cout << 0;
        return 0;
    }
    if(n == 2){
        if(col[1] == col[2]){
            cout << 0 << "\n";
        }else cout << 1 << "\n";
        return 0;
    }
    in[n + 1] = n + 1;
    pre(root, 0);
     for(int i = 1; i <= k; i ++){
        if(vr[i].empty()) continue;

        sort(all(vr[i]), [&] (int x,int y){return in[x] < in[y];});
        int mi = vr[i][0];
        for(int j = 0; j < vr[i].size() - 1; j ++){
            int u = lca(vr[i][j], vr[i][j + 1]);
            if(in[u] < in[mi]) mi = u;
        }
        open[mi].pb(i);
    }
    dfs(root, 0);
    for(int i = 1; i <= n; i ++){
        for(auto j : p[i]) if(fin(j) != fin(i)) g[fin(i)]++, g[fin(j)]++;
    }
    for(int i = 1; i <= n; i ++) if(g[i] == 2) ans++;
    cerr << (ans + 1) / 2 << "\n";
   cout << (ans + 1) / 2;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:144:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  144 |         for(int j = 0; j < vr[i].size() - 1; j ++){
      |                        ~~^~~~~~~~~~~~~~~~~~
mergers.cpp:108:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  108 |         freopen(task ".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
mergers.cpp:109:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  109 |         freopen(task ".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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