Submission #1078157

#	Time	Username	Problem	Language	Result	Execution time	Memory
1078157		hung_nm	Pipes (BOI13_pipes)	C++17	100 / 100	178 ms	57652 KiB

pipes

#include <bits/stdc++.h>
#define pb push_back
#define fi first
#define se second
#define pii pair<int, int>
#define pipii pair<int, pair<int, int>>
#define vi vector<int>
#define vpi vector<pair<int, int>>
#define inp(name) if(fopen(name, "r")) freopen(name, "r", stdin);
#define out(name) if(fopen(name, "w")) freopen(name, "w", stdout);
#define int long long
const int N = 1e6 + 5;
const int mod = 1e9 + 7;
using namespace std;

long long n, m, c[N], ans[N];
vpi ad[N];

void dfs(int u, int p, int id = 0)
{
    long long res = 0;
    for (auto [v, pos] : ad[u])
    {
        if (v == p) continue;
        dfs(v, u, pos);
        res += ans[pos];
    }
    ans[id] = c[u] - res;
}

void sub1()
{
    dfs(1, 0);
    for (int i = 1; i <= m; ++i)
    {
        cout << 2 * ans[i] << "\n";
    }
}

long long del[N], deg[N], ok[N], tmp, x, root, root2, id;
queue<int> q;

void dfs2(int u, int p, int dau)
{
    ok[u] = 1;
    tmp = tmp + dau * c[u];
    for (auto [v, i] : ad[u])
    {
        if (v == p || del[v])
        {
            continue;
        }
        if(ok[v] == 0)
        {
            dfs2(v, u, dau * (-1));
            if (x != 0)
            {
                return;
            }
        }
        else
        {
            ans[id] = tmp;
            return ;
        }
    }
}

void dfs3(int u, int p, int pre)
{
    ok[u] = 1;
    for (auto [v, i] : ad[u])
    {
        if (v == p || del[v] || ok[v]) continue;
        ans[i] = 2 * c[u] - ans[pre];
        dfs3(v, u, i);
    }
}

void sub2()
{
    for (int i = 1; i <= n; ++i)
    {
        if (deg[i] == 1)
        {
            q.push(i);
            del[i] = 1;
        }
    }

    while (!q.empty())
    {
        int u = q.front(); q.pop();
        del[u] = 1;
        for (auto [v, i] : ad[u])
        {
            if (del[v]) continue;
            ans[i] = 2 * c[u];
            c[v] -= c[u];
            deg[v]--;
            if (deg[v] == 1)
            {
                q.push(v);
            }
        }
    }
    long long cnt = 0;
    for(int i = 1; i <= n; ++i)
    {
        if(!del[i])
        {
            root = i;
            cnt++;
        }
    }

    if(cnt % 2 == 0)
    {
        cout << 0;
        return ;
    }


    for(auto [x, i] : ad[root])
    {
        if(del[x]) continue ;
        root2 = x;
        id = i;
        break ;
    }

    ok[root] = 1;
    dfs2(root, root2, 1);
    memset(ok, 0, sizeof(ok));
    dfs3(root, root2, id);
    for (int i = 1; i <= m; ++i)
    {
        cout << ans[i] << "\n";
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n; ++i)
    {
        cin >> c[i];
    }

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

    if (m > n)
    {
        cout << 0;
        return 0;
    }

    if (m == (n - 1))
    {
        sub1();
        return 0;
    }

    sub2();
    return 0;
}

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