Submission #913952

#	Time	Username	Problem	Language	Result	Execution time	Memory
913952		a_l_i_r_e_z_a	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	376 ms	33848 KiB

commuter_pass

// In the name of God
// Hope is last to die

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

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;

#define pb push_back
#define S second
#define F first
#define mp make_pair
#define smax(x, y) (x) = max((x), (y))
#define smin(x, y) (x) = min((x), (y))
#define all(x) (x).begin(), (x).end()
#define len(x) ((int)(x).size())

const int maxn = 1e5 + 5;
const ll inf = 1e18 + 7;
ll n, m, s, t, x, y, ans = inf, d[maxn][3], dp[maxn][3];
set<pll> st;
vector<pll> adj[maxn];
vector<int> g[maxn];
bool mark[maxn];

void dij(int v, int ind){
    st.clear();
    st.insert(mp(0, v));
    d[v][ind] = 0;
    while(st.size()){
        ll v = (*st.begin()).S, dist = (*st.begin()).F;
        st.erase(st.begin());
        for(auto [u, w]: adj[v]){
            if(d[v][ind] + w < d[u][ind]){
                st.erase(mp(d[u][ind], u));
                d[u][ind] = d[v][ind] + w;
                st.insert(mp(d[u][ind], u));
            }
        }
    }
}

void dfs(int v){
    mark[v] = 1;
    dp[v][1] = dp[v][2] = inf;
    for(auto u: g[v]){
        if(!mark[u]) dfs(u);
        smin(dp[v][1], dp[u][1]);
        smin(dp[v][2], dp[u][2]);
    }
    if(dp[v][1] == inf){
        if(v == t){
            dp[v][1] = d[v][1];
            dp[v][2] = d[v][2];
        }
    }
    else{
        smin(dp[v][1], d[v][1]);
        smin(dp[v][2], d[v][2]);
    }
    smin(ans, d[v][1] + dp[v][2]);
    smin(ans, d[v][2] + dp[v][1]);
}

int32_t main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    memset(d, 63, sizeof d);
    cin >> n >> m >> s >> t >> x >> y;
    for(int i = 1; i <= m; i++){
        int u, v, w; cin >> u >> v >> w;
        adj[u].pb(mp(v, w));
        adj[v].pb(mp(u, w));
    }
    dij(s, 0);
    dij(x, 1);
    dij(y, 2);
    for(int i = 1; i <= n; i++){
        for(auto [u, w]: adj[i]){
            if(d[i][0] + w == d[u][0]) g[i].pb(u);
        }
    }
    dfs(s);
    cout << min(ans, d[y][1]) << '\n';

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'void dij(int, int)':
commuter_pass.cpp:34:33: warning: unused variable 'dist' [-Wunused-variable]
   34 |         ll v = (*st.begin()).S, dist = (*st.begin()).F;
      |                                 ^~~~

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