Submission #894685

#	Time	Username	Problem	Language	Result	Execution time	Memory
894685		Andrey	Mergers (JOI19_mergers)	C++14	100 / 100	1150 ms	153252 KiB

mergers

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

vector<int> haha[500001];
vector<int> col[500001];
vector<int> dep(500001);
vector<int> br(500001);
vector<int> wow[500001];
int bruh[500001][20];

int lca(int a, int b) {
    if(dep[a] < dep[b]) {
        swap(a,b);
    }
    int c = dep[a]-dep[b];
    for(int i = 19; i >= 0; i--) {
        if((1 << i)&c) {
            a = bruh[a][i];
        }
    }
    for(int i = 19; i >= 0; i--) {
        if(bruh[a][i] != -1 && bruh[a][i] != bruh[b][i]) {
            a = bruh[a][i];
            b = bruh[b][i];
        }
    }
    if(a == b) {
        return a;
    }
    else {
        return bruh[a][0];
    }
}

void dfs(int a, int t, int d) {
    dep[a] = d+1;
    bruh[a][0] = t;
    for(int v: haha[a]) {
        if(v != t) {
            dfs(v,a,d+1);
        }
    }
}

void dude(int a, int t) {
    for(int v: haha[a]) {
        if(v != t) {
            dude(v,a);
            br[a]+=br[v];
        }
    }
}

void banana(int a, int t, int l) {
    if(br[a] == 0) {
        if(l != -1) {
            wow[a].push_back(l);
            wow[l].push_back(a);
        }
        l = a;
    }
    for(int v: haha[a]) {
        if(v != t) {
            banana(v,a,l);
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int n,k,a,b;
    cin >> n >> k;
    for(int i = 0; i < n-1; i++) {
        cin >> a >> b;
        haha[a].push_back(b);
        haha[b].push_back(a);
    }
    dfs(1,-1,0);
    for(long long i = 1; i < 20; i++) {
        for(long long j = 1; j <= n; j++) {
            if(bruh[j][i-1] == -1) {
                bruh[j][i] = -1;
            }
            else {
                bruh[j][i] = bruh[bruh[j][i-1]][i-1];
            }
        }
    }
    for(int i = 1; i <= n; i++) {
        cin >> a;
        col[a].push_back(i);
    }
    for(int i = 1; i <= k; i++) {
        int c = col[i][0];
        for(int v: col[i]) {
            br[v]++;
            c = lca(c,v);
        }
        br[c]-=col[i].size();
    }
    dude(1,-1);
    banana(1,-1,-1);
    int ans = 0;
    for(int i = 1; i <= n; i++) {
        if(wow[i].size() == 1) {
            ans++;
        }
    }
    if(ans == 1) {
        cout << 0;
    }
    else {
        cout << (ans+1)/2;
    }
    return 0;
}

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