제출 #556368

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
556368		Olympia	Mag (COCI16_mag)	C++17	0 / 120	1008 ms	195004 KiB

mag

#include <bits/stdc++.h>
using namespace std;
vector<int> val;
vector<int> parent;
vector<int> dp1, dp2, dp3;
//dp1 is the maximum path that goes down
//dp2 is the maximum path that does not necessarily go down
//dp3 is the maximum path that goes up (straight up)
void dfs (vector<vector<int> > &adj, int curNode, int prevNode) {
    dp1[curNode] = (val[curNode] == 1);
    for (int i: adj[curNode]) {
        if (i != prevNode) {
            dfs (adj, i, curNode);
            dp1[curNode] = max(dp1[curNode], dp1[i] + 1);
        }
    }
    if (val[curNode] != 1) {
        dp1[curNode] = 0;
    }
}
void dfs2 (vector<vector<int> > &adj, int curNode, int prevNode) {
    parent[curNode] = prevNode;
    dp2[curNode] = dp1[curNode];
    vector<int> v;
    for (int i: adj[curNode]) {
        if (i != prevNode) {
            dfs2(adj, i, curNode);
            v.push_back(dp1[i]);
        }
    }
    sort(v.begin(), v.end());
    if (v.size() >= 2) {
        dp2[curNode] = max(dp2[curNode], v.back() + v[v.size() - 2] + 1);
    }
    if (val[curNode] != 1) {
        dp2[curNode] = 0;
    }
}

void dfs3 (vector<vector<int> >&adj, int curNode, int prevNode) {
    if (curNode != prevNode) {
        dp3[curNode] = dp3[prevNode] + 1;
    } else {
        dp3[curNode] = 1;
    }
    if (val[curNode] != 1) {
        dp3[curNode] = 0;
    }
    for (int i: adj[curNode]) {
        if (i != prevNode) {
            dfs3(adj, i, curNode);
        }
    }
}

int main() {
    vector<vector<int> > adj;
    int n;
    cin >> n;
    adj.resize(n), dp1.resize(n), dp2.resize(n), dp3.resize(n), parent.resize(n);
    for (int i = 0; i < n - 1; i++) {
        int u, v;
        cin >> u >> v;
        u--, v--;
        adj[u].push_back(v), adj[v].push_back(u);
    }
    val.resize(n);
    int myMin = INT_MAX;
    for (int i = 0; i < n; i++) {
        cin >> val[i];
        myMin = min(myMin, val[i]);
    }
    if (myMin >= 2) {
        cout << myMin << "/" << 1;
        return 0;
    }
    dfs(adj, 0, 0);
    dfs2(adj, 0, 0);
    dfs3(adj, 0, 0);
    int myMax2 = 0;
    int myMax1 = 0;
    for (int i = 0; i < n; i++) {
        myMax1 = max(myMax1, dp2[i]);
        if (val[i] == 2) {
            vector<int> v;
            for (int j: adj[i]) {
                if (j == parent[i]) {
                    v.push_back(dp3[j]);
                } else {
                    v.push_back(dp1[j]);
                }
            }
            sort(v.begin(), v.begin());
            reverse(v.begin(), v.end());
            myMax2 = max(myMax2, v[0]);
            if (v.size() >= 2) myMax2 = max(myMax2, v[0] + v[1]);
            myMax2++;
        }
    }
    cout << 2 << "/" << myMax2 << '\n';

}

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