Submission #860645

#	Time	Username	Problem	Language	Result	Execution time	Memory
860645		Nursik	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	218 ms	31380 KiB

commuter_pass

#include <stdio.h>

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <random>
#include <chrono>
#include <queue>
#include <functional>
#include <iostream>
#include <queue>
//#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define ld long double

const ll maxn = 1e5 + 1, maxm = 1e7 + 1;
const ll mod = 1e9 + 7, mod2 = 998244353, inf = 1e9, block = 550, hb = 31, base = 1000050017;
const ld eps = 1e-9;

int n, m;
int s, t;
int ss, tt;
bool is[maxn];
int go[maxn];
ll ans = inf * inf, dp[maxn], dp2[maxn], dp3[maxn], was[maxn];
ll pd[maxn][2];
vector<pair<int, int>> g[maxn];
vector<int> g2[maxn], g3[maxn];
void dfsis(int v){
    if (v == t){
        is[v] = 1;
    }
    was[v] = 1;
    for (auto to : g2[v]){
        if (was[to] == 0){
            dfsis(to);
        }
        is[v] |= is[to];
    }
}

void dijkstra(){
    for (int i = 1; i <= n; ++i){
        dp[i] = inf * inf;
    }
    dp[s] = 0;
   // set<pair<ll, int>> setik;
    priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>> > setik;
    setik.push(mp(0, s));
    while (setik.size() > 0){
        pair<ll, int> cur = setik.top();
        setik.pop();
        ll cost = cur.f, v = cur.s;
        if (dp[v] < cost){
            continue;
        }
        for (auto to : g[v]){
            int nv = to.f, w = to.s;
            if (dp[nv] > cost + w){
                dp[nv] = cost + w;
                setik.push(mp(dp[nv], nv));
            }
        }
    }
    for (int i = 1; i <= n; ++i){
        for (auto to : g[i]){
            int nv = to.f, w = to.s;
            if (dp[i] > dp[nv]){
                continue;
            }
            if (dp[nv] == w + dp[i] && dp[i] < dp[nv]){
                g2[i].pb(nv);
            }
        }
    }
    dfsis(s);

    for (int i = 1; i <= n; ++i){
        g2[i].clear();
        for (auto to : g[i]){
            int nv = to.f, w = to.s;
            if (dp[i] > dp[nv]){
                continue;
            }
            if (dp[nv] == w + dp[i] && is[nv] == 1){
                g2[i].pb(nv);
            }
        }
    }
}
void dijkstra2(){
    for (int i = 1; i <= n; ++i){
        dp2[i] = inf * inf;
    }
    dp2[ss] = 0;
  //  set<pair<ll, int>> setik;
    priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>> > setik;
    setik.push(mp(0, ss));
    while (setik.size() > 0){
        pair<ll, int> cur = setik.top();
        setik.pop();
        ll cost = cur.f, v = cur.s;
        if (dp2[v] < cost){
            continue;
        }
        for (auto to : g[v]){
            int nv = to.f, w = to.s;
            if (dp2[nv] > cost + w){
                dp2[nv] = cost + w;
                setik.push(mp(dp2[nv], nv));
            }
        }
    }
}
void dijkstra3(){
    for (int i = 1; i <= n; ++i){
        dp3[i] = inf * inf;
    }
    dp3[tt] = 0;
    priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>> > setik;
    setik.push(mp(0, tt));
    while (setik.size() > 0){
        pair<ll, int> cur = setik.top();
        setik.pop();
        ll cost = cur.f, v = cur.s;
        if (dp3[v] < cost){
            continue;
        }
        for (auto to : g[v]){
            int nv = to.f, w = to.s;
            if (dp3[nv] > cost + w){
                dp3[nv] = cost + w;
                setik.push(mp(dp3[nv], nv));
            }
        }
    }
}

void backdfs(int v){
    for (int i = 1; i <= n; ++i){
        for (auto to : g2[i]){
            go[i] += 1;
            g3[to].pb(i);
        }
        pd[i][0] = inf * inf;
        pd[i][1] = inf * inf;
    }

    queue<int> q;
    q.push(v);
    while (q.size() > 0){
        int u = q.front();
        q.pop();
        pd[u][0] = min(pd[u][0], dp3[u]);
        pd[u][1] = min(pd[u][1], dp2[u]);

        ans = min(ans, pd[u][0] + dp2[u]);
        ans = min(ans, pd[u][1] + dp3[u]);
        for (auto to : g3[u]){
            go[to] -= 1;
            pd[to][0] = min(pd[to][0], pd[u][0]);
            pd[to][1] = min(pd[to][1], pd[u][1]);
            if (go[to] == 0){
                q.push(to);
            }
        }
    }
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    cin >> s >> t;
    cin >> ss >> tt;
    
    for (int i = 1; i <= m; ++i){
        int a, b, c;
        cin >> a >> b >> c;
        g[a].pb(mp(b, c));
        g[b].pb(mp(a, c));
    }
    dijkstra();
    dijkstra2();
    dijkstra3();
    backdfs(t);
    ans = min(ans, dp2[tt]);
    cout << ans << '\n';
}

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