Submission #926783

#	Time	Username	Problem	Language	Result	Execution time	Memory
926783		LonlyR	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	211 ms	42140 KiB

commuter_pass

#include<bits/stdc++.h>
#define int long long
#define ii pair<int,int>
#define ff first
#define ss second

using namespace std;
const int maxn = 2e5 + 5;
int n, m, s, t, a, b, ans = 1e18;
int d[4][maxn], vis[maxn];
ii dp[maxn];
vector<ii> adj[maxn];
vector<int> dag[maxn];

void bfs(int x) /// dijkstra
{
    int y;
    if (x == t) y = 1;
    else if (x == a) y = 2;
    else y = 3;
    memset(d[y], 0x3f, sizeof d[y]);
    d[y][x] = 0;
    priority_queue<ii, vector<ii>, greater<ii>> pq;
    pq.emplace(0, x);
    while (pq.size())
    {
        int u, v;
        tie(v, u) = pq.top();
        pq.pop();
        if (v != d[y][u]) continue;
        for (auto p : adj[u])
            if (d[y][p.ff] > v + p.ss)
                pq.emplace(d[y][p.ff] = v + p.ss, p.ff);
    }
}

void dfs(int x)
{
    if (vis[x]) return;
    vis[x] = 1;
    for (auto p : adj[x])
        if (d[1][x] == d[1][p.ff] + p.ss)
            dag[x].emplace_back(p.ff),
            dfs(p.ff);
}

ii cal(int x)
{
    if (vis[x]) return dp[x];
    vis[x] = 1;
    dp[x].ff = d[3][x];
    dp[x].ss = d[2][x];
    for (int i : dag[x])
    {
        int u, v;
        tie(u, v) = cal(i);
        dp[x].ff = min(dp[x].ff, u);
        dp[x].ss = min(dp[x].ss, v);
    }
    ans = min(ans, d[2][x] + dp[x].ff);
    ans = min(ans, d[3][x] + dp[x].ss);
    return dp[x];
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
//    freopen("test.inp", "r", stdin);
//    freopen("test.out", "w", stdout);
    cin >> n >> m >> s >> t >> a >> b;
    for (int i = 1, u, v, w; i <= m; i++)
        cin >> u >> v >> w,
        adj[u].emplace_back(v, w),
        adj[v].emplace_back(u, w);
    bfs(t);
    bfs(a);
    bfs(b);
    dfs(s);
    memset(vis, 0, sizeof vis);
    cal(s);
    ans = min(ans, d[2][b]);
    cout << ans;
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45