Submission #539233

#	Time	Username	Problem	Language	Result	Execution time	Memory
539233		nafis_shifat	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	30 ms	7876 KiB

ho_t4

#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
using namespace std;
const int mxn=2e5+5;
const ll INF=1e18;
int n,m;
int l[mxn], r[mxn];
ll c[mxn], d[mxn];
vector<int> adj[mxn];

bool blocked[mxn] = {};
bool used[mxn] = {};
void dijkstra(int s, vector<ll> &d, vector<int> & p) {
    
    d.assign(n + 1, INF);
    p.assign(n + 1, -1);
    vector<bool> u(n, false);

    d[s] = 0;
    for(int i = 1; i <= n; i++) {
        int v = -1;
        for (int j = 1; j <= n; j++) {
            if (!u[j] && (v == -1 || d[j] < d[v]))
                v = j;
        }

        if(d[v] == INF)
            break;

        u[v] = true;
        for (auto edge : adj[v]) {
        	if(blocked[edge]) continue;
            int to = l[edge] ^ r[edge] ^ v;
            ll len = c[edge];

            if (d[v] + len < d[to]) {
                d[to] = d[v] + len;
                p[to] = edge;
            }
        }
    }
}



int main() {
	cin >> n >> m;

	ll w[n + 1][n + 1];
	for(int i = 1; i <= n; i++) for(int j = 1; j <= n; j++) {
		if(i == j) w[i][j] = 0;
		else w[i][j] = INF;
	}

	for(int i = 1; i <= m; i++) {
		scanf("%d%d%lld%lld",&l[i],&r[i],&c[i],&d[i]);
		adj[l[i]].push_back(i);
		// adj[1][r[i]].push_back(i);
		w[l[i]][r[i]] = min(w[l[i]][r[i]], c[i]);
	}

	for(int k = 1; k <= n; k++) {
		for(int i = 1; i <= n; i++) {
			for(int j = 1; j <= n; j++) {
				w[i][j] = min(w[i][j], w[i][k] + w[k][j]);
			}
		}
	}



	ll ans = w[1][n] + w[n][1];
	
	int source = 1;
	int target = n;
	
	if(w[1][n] >= INF) {
	    swap(source, target);
	    if(w[source][target] >= INF) {
	        for(int i = 1; i <= m; i++) {
	        	ans = min(ans, d[i] + w[1][r[i]] + c[i] + w[l[i]][n] + w[n][r[i]] + c[i] + w[l[i]][1]);
	        }

	        if(ans >= INF) cout<<-1<<endl;
	        else cout<<ans<<endl;
	        return 0;
	    }
	}
	
	


	vector<ll> dist1, dist2;
	vector<int> last1, last2;
	dijkstra(source, dist1, last1);
	

	vector<int> sedg;
	
	
	
	int nd = target;

	while(nd != source) {
	    
		used[last1[nd]] = true;
		sedg.push_back(last1[nd]);
		nd = l[last1[nd]];
	}


	for(int i = 1; i <= m; i++) {
		if(used[i]) continue;
		ans = min(ans, w[source][target] + w[target][r[i]] + d[i] + c[i] + w[l[i]][source]);
	}

	for(int i : sedg) {
		blocked[i] = true;
		vector<int> cl;
		l[m + 1] = r[i];
		r[m + 1] = l[i];
		c[m + 1] = c[i];

		adj[l[m + 1]].push_back(m + 1);

		dijkstra(source, dist1, cl);
		dijkstra(target, dist2, cl);
		ans = min(ans, dist1[target] + dist2[source]);
		blocked[i] = false;
		adj[l[m + 1]].pop_back();
	}

	cout<<ans<<endl;








	
}

Compilation message (stderr)

ho_t4.cpp: In function 'int main()':
ho_t4.cpp:57:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |   scanf("%d%d%lld%lld",&l[i],&r[i],&c[i],&d[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63