Submission #1051047

#	Time	Username	Problem	Language	Result	Execution time	Memory
1051047		ortsac	Pipes (BOI13_pipes)	C++17	74.07 / 100	95 ms	39436 KiB

pipes

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

#define int long long
#define pii pair<long long, long long>
#define fr first
#define se second

const int MAXN = 1e5 + 10;
const int MAXM = 5e5 + 10;
vector<pii> adj[MAXN];
int bEdge = -1;
vector<pii> edges;
int h[MAXN];
int change[MAXN];
bool vis[MAXN];
int dad[MAXN];
int dp[MAXN];
int peso[MAXM];

void dfs(int node) {
    vis[node] = 1;
    for (auto [u, z] : adj[node]) {
        if (u == dad[node]) continue;
        if (vis[u]) bEdge = z;
        else {
            dad[u] = node;
            h[u] = h[node] + 1;
            dfs(u);
        }
    }
}

void calc(int node) {
    vis[node] = 1;
    for (auto [u, z] : adj[node]) {
        if (vis[u]) continue;
        calc(u);
        dp[node] += (change[u] - dp[u]);
        peso[z] += (change[u] - dp[u]);
    }
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++) cin >> change[i];
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        edges.push_back({a, b});
        adj[a].push_back({b, i});
        adj[b].push_back({a, i});
    }
    if (m > n) {
        cout << "0\n";
        return 0;
    }
    dfs(1);
    int lca = 0;
    if (bEdge != -1) {
        auto u = edges[bEdge];
        int a = u.fr, b = u.se;
        if (h[a] > h[b]) swap(a, b);
        // a is higher than b
        int oa = a, ob = b;
        while (h[b] > h[a]) {
            b = dad[b];
        }
        while (a != b) {
            a = dad[a];
            b = dad[b];
        }
        lca = a;
        a = oa;
        b = ob;
        int tam = h[a] + h[b] - 2*h[lca] + 1;
        if ((tam % 2LL) == 0) {
            cout << "0\n";
            return 0;
        }
    }
    memset(vis, 0, sizeof vis);
    calc(1);
    if (dp[1] == change[1]) {
        for (int i = 0; i < m; i++) cout << 2*peso[i] << "\n";
        return 0;
    }
    // first case is for tree
    // second case is if you can't add 2x to it
    if ((bEdge == -1)) {
        cout << "0\n";
        return 0;
    }
    //cout << "0\n";
}

• Subtask 1: 30 / 30
• Subtask 2: 44.074074074074076 / 70