Submission #949633

#	Time	Username	Problem	Language	Result	Execution time	Memory
949633		ace5	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	386 ms	30188 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

const int maxn = 100001;
const int64_t INF = 1e18;

vector<pair<int,int>> g[maxn];
vector<int> g2[maxn];
vector<int> g3[maxn];
vector<int> ts;
int64_t dp[maxn];
int64_t d[maxn],ds[maxn],dt[maxn],du[maxn],dv[maxn];
int vis[maxn];
set<pair<int64_t,int>> ff;
int n;

void dij(int s)
{
    for(int j = 0;j < n;++j)
    {
        d[j] = INF;
        vis[j] = 0;
    }
    d[s] = 0;
    ff.insert({0,s});
    while(ff.size())
    {
        int v = (*ff.begin()).second;
        ff.erase(ff.begin());
        vis[v] = 1;
        for(auto [u,dd]:g[v])
        {
            if(d[u] > d[v] + dd && !vis[u])
            {
                ff.erase({d[u],u});
                d[u] = d[v] + dd;
                ff.insert({d[u],u});
            }
        }
    }
    return ;
}
void dfs(int v)
{
    vis[v] = 1;
    for(auto u:g2[v])
    {
        if(!vis[u])
        {
            dfs(u);
        }
    }
    ts.push_back(v);
    return ;
}
void dfs2(int v)
{
    vis[v] = 1;
    for(auto u:g3[v])
    {
        if(!vis[u])
        {
            dfs2(u);
        }
    }
    ts.push_back(v);
    return ;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int m;
    cin >> n >> m;
    int s,t,u,v;
    cin >> s >> t >> u >> v;
    s--;
    t--;
    u--;
    v--;
    for(int i = 0;i < m;++i)
    {
        int a,b,c;
        cin >> a >> b >> c;
        a--;
        b--;
        g[a].push_back({b,c});
        g[b].push_back({a,c});
    }
    dij(s);
    for(int j = 0;j < n;++j)
    {
        ds[j] = d[j];
    }
    dij(t);
    for(int j = 0;j < n;++j)
    {
        dt[j] = d[j];
    }
    dij(u);
    for(int j = 0;j < n;++j)
    {
        du[j] = d[j];
    }
    dij(v);
    for(int j = 0;j < n;++j)
    {
        dv[j] = d[j];
    }
    for(int v = 0;v < n;++v)
    {
        for(auto [u,d] : g[v])
        {
            if(ds[u]-ds[v] == d && dt[v]-dt[u] == d && ds[u] + dt[u] == ds[t])
            {
                g2[v].push_back(u);
                g3[u].push_back(v);
            }
        }
    }
    for(int i = 0;i < n;++i)
        vis[i] = 0;
    dfs(s);
    int64_t ans = du[v];
    for(int i = 0;i < ts.size();++i)
    {
        dp[ts[i]] = dv[ts[i]];
        for(auto u : g2[ts[i]])
        {
            dp[ts[i]] = min(dp[ts[i]],dp[u]);
        }
        ans = min(ans,dp[ts[i]]+du[ts[i]]);
    }
    for(int i = 0;i < n;++i)
        vis[i] = 0;
    ts.clear();
    dfs2(t);
    for(int i = 0;i < ts.size();++i)
    {
        dp[ts[i]] = dv[ts[i]];
        for(auto u : g3[ts[i]])
        {
            dp[ts[i]] = min(dp[ts[i]],dp[u]);
        }
        ans = min(ans,dp[ts[i]]+du[ts[i]]);
    }
    cout << ans << "\n";
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:127:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  127 |     for(int i = 0;i < ts.size();++i)
      |                   ~~^~~~~~~~~~~
commuter_pass.cpp:140:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  140 |     for(int i = 0;i < ts.size();++i)
      |                   ~~^~~~~~~~~~~

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