Submission #673746

#	Time	Username	Problem	Language	Result	Execution time	Memory
673746		MilosMilutinovic	Olympic Bus (JOI20_ho_t4)	C++14	100 / 100	957 ms	3676 KiB

ho_t4

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}());
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=202;
const int M=50500;
const ll inf=1e18;

int n,m,u[M],v[M],c[M],d[M],prv[2][N];
ll dis[2][N],f[N][N];
bool is[M];
vector<array<int,3>> e[N];

void dijkstra(int v,ll* d,int* pp) {
	rep(i,1,n+1) d[i]=inf;
	d[v]=0; pp[v]=-1;
	priority_queue<pair<ll,int>> pq;
	pq.push({0,v});
	while (SZ(pq)) {
		int i=pq.top().second;
		ll dd=-pq.top().first;
		pq.pop();
		if (dd>d[i]) continue;
		for (auto& p:e[i]) {
			int j=p[0],w=p[1];
			if (d[j]>d[i]+w) {
				d[j]=d[i]+w; pp[j]=p[2];
				pq.push({-d[j],j});
			}
		}
	}
}

ll solve(int id) {
	rep(i,1,n+1) e[i].clear();
	rep(i,0,m) {
		if (i==id) e[v[i]].pb({u[i],c[i],i});
		else e[u[i]].pb({v[i],c[i],i});
	}
	dijkstra(1,dis[0],prv[0]);
	dijkstra(n,dis[1],prv[1]);
	return dis[0][n]+dis[1][1]+d[id];
}

int main() {
	scanf("%d%d",&n,&m);
	rep(i,1,n+1) rep(j,1,n+1)
		f[i][j]=inf;
	rep(i,0,m) {
		scanf("%d%d%d%d",u+i,v+i,c+i,d+i);
		e[u[i]].pb({v[i],c[i],i});
		f[u[i]][v[i]]=min(f[u[i]][v[i]],(ll)c[i]);
	}
	rep(i,1,n+1) f[i][i]=0;
	rep(k,1,n+1) rep(i,1,n+1) rep(j,1,n+1)
		f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
	dijkstra(1,dis[0],prv[0]);
	dijkstra(n,dis[1],prv[1]);
	rep(j,0,2) rep(i,1,n+1) if (prv[j][i]!=-1)
		is[prv[j][i]]=1;
	ll ans=dis[0][n]+dis[1][1];
	rep(i,0,m) {
		if (is[i]) {
			ans=min(ans,solve(i));
		} else {
			ll d1=min(f[1][n],f[1][v[i]]+c[i]+f[u[i]][n]);
			ll d2=min(f[n][1],f[n][v[i]]+c[i]+f[u[i]][1]);
			ans=min(ans,d1+d2+d[i]);
		}
	}
	if (ans>=inf) ans=-1;
	printf("%lld",ans);
}

Compilation message (stderr)

ho_t4.cpp: In function 'int main()':
ho_t4.cpp:65:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |  scanf("%d%d",&n,&m);
      |  ~~~~~^~~~~~~~~~~~~~
ho_t4.cpp:69:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |   scanf("%d%d%d%d",u+i,v+i,c+i,d+i);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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