Submission #1241928

#	Time	Username	Problem	Language	Result	Execution time	Memory
1241928		sunit	Commuter Pass (JOI18_commuter_pass)	C++20	0 / 100	2098 ms	75232 KiB

commuter_pass

#include<bits/stdc++.h>
#define int long long
#define bl bool
#define db double 
#define fl float 
#define st string 
#define pb push_back
#define pf push_front
#define is insert
#define endl "\n"
#define pba pop_back
#define pfr pop_front
#define ub upper_bound
#define lb lower_bound 
#define fi first 
#define se second 
#define FOR(i, l, r, st) for(int i = l; i <= r; i += st)
#define FOS(i, l, r, sl) for(int i = l; i >= r; i -= sl)
#define mii map<int, int>
#define us unordered_set 
#define pii pair<int, int>
#define vt vector
using namespace std;

const int maxn = 1e6 + 5;

const int mod = 1e9 + 7;

void suncuti() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
}

void fre() {
    if(fopen("name.INP", "r")) {
        freopen("name.INP", "r", stdin);
        freopen("name.OUT", "w", stdout);
    }
}

int n, m, A, B, C, D;

vt<pii>kt[maxn];

int trace[maxn];

map<pii, int>seen;

int dp[maxn];

void dij() {
    fill(dp, dp + maxn, 1e18);
    memset(trace, -1, sizeof(trace));
    dp[A] = 0;
    priority_queue<pii, vt<pii>, greater<pii>>q;
    q.push({0, A});
    while(q.size()) {
        int c = q.top().fi, u = q.top().se;
        q.pop();
        if(c > dp[u]) continue;
        for(auto v : kt[u]) {
            int cost = v.se + dp[u];
            if(cost < dp[v.fi]) {
                dp[v.fi] = cost;
                trace[v.fi] = u;
                q.push({dp[v.fi], v.fi});
            }
        }
    }
}

vt<int>path;

void bfs() {
    fill(dp, dp + maxn, 1e18);
    dp[C] = 0;
    deque<int>d;
    d.pf(C);
    while(d.size()) {
        int u = d.front();
        d.pfr();
        for(auto v : kt[u]) {
            int cost = dp[u];
            if(seen[{v.fi, u}] || seen[{u, v.fi}]) cost = cost;
            else cost = cost + v.se;
            if(cost < dp[v.fi]) {
                dp[v.fi] = cost;
                if(!cost) d.pf(v.fi);
                else d.pb(v.fi);
            }
        }
    }
}

main() {
    suncuti();

    cin >> n >> m;

    cin >> A >> B;

    cin >> C >> D;

    FOR(i, 1, m, 1) {
        int u, v, w;

        cin >> u >> v >> w;

        kt[u].pb({v, w});

        kt[v].pb({u, w});
    }

    dij();

    int kit = B;

    while(kit != -1) {
        path.pb(kit);
        kit = trace[kit];
    }

    reverse(path.begin(), path.end());

    FOR(i, 1, path.size() - 1, 1) {
        // cout << path[i] << " ";
        seen[{path[i], path[i - 1]}] = seen[{path[i - 1], path[i]}] = 1;
    }

    bfs();

    cout << dp[D];
}

Compilation message (stderr)

commuter_pass.cpp:96:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   96 | main() {
      | ^~~~
commuter_pass.cpp: In function 'void fre()':
commuter_pass.cpp:37:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |         freopen("name.INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:38:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |         freopen("name.OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 16
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45