Submission #1316849

#TimeUsernameProblemLanguageResultExecution timeMemory
1316849WH8Olympic Bus (JOI20_ho_t4)C++17
0 / 100
173 ms9844 KiB
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pll pair<long long, long long>
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define endl '\n'
#define ld long double
#define sz(x) static_cast<int>((x).size())
#define i5 tuple<int,int,int,int,int>
#define all(x) x.begin(), x.end()
#define iiii tuple<int, int,int,int>
#define ld long double
#define lol pair<pll,pll>
#define iii tuple<int,int,int>
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
int n,m;
vector<vector<iii>> al(205), tal(205);
vector<tuple<int,int,int,int>> ed;

pair<vector<int>, vector<int>> dijk(int s, int skip, vector<vector<iii>> & aa){
	vector<int> pdist(n+1, 1e15), dist(n+1, 1e15), from(n+1, -1), ways(n+1, 0);
	pdist[s]=0;
	ways[s]=1;
	for(int i=0;i<n;i++){
		pll mn=mp((int)1e16,0);
		for(int i=1;i<=n;i++){
			mn=min(mn, mp(pdist[i], i));
		}
		//printf("relaxing %lld, %lld\n", mn.f, mn.s);
		if (dist[mn.s] < pdist[mn.s]) continue;
		dist[mn.s]=pdist[mn.s];
		//for(int j=1;j<=n;j++){cout<<dist[j]<<" ";} cout<<endl;
		pdist[mn.s]=1e15;
		int d=dist[mn.s], c=mn.s;
		for(auto [to,w,ind]:aa[c]){
			if(dist[to]<d+w or pdist[to]<d+w or ind==skip)continue;
			if(dist[to] > d+w and pdist[to] > d+w){
				assert(dist[to] == 1e15);
				pdist[to]=d+w;
				from[to]=ind;
			}
		}
	}
	return mp(dist, from);
}

signed main(){
	cin>>n>>m;
	for(int i=0;i<m;i++){
		int a,b,c,d;cin>>a>>b>>c>>d;
		ed.pb({a,b,c,d});
		al[a].pb({b,c,i});
		tal[b].pb({a,c,i});
	}
	vector<vector<int>> anw(m+1), bnw(m+1);
	auto [an, af] = dijk(1, m, al);
	auto [at, atf] = dijk(1, m, tal);
	auto [bn, bf] = dijk(n, m, al);
	auto [bt, btf] = dijk(n, m, tal);
	vector<bool> ona(m+1, 0), onb(m+1, 0);
	/*for(int i=1;i<=n;i++){
		printf("dist from 1 of i %lld is %lld, ways %lld, from %lld\n", i, at[i],aw[i], af[i]);
		printf("dist from n of i %lld is %lld, ways %lld, from %lld\n", i, bt[i],bw[i], bf[i]);
	}*/
	int cnt=0;
	int ce=af[n];
	while(ce != -1){
		//if(cnt++ > 5)return 0;
		//printf("an, path ce %lld\n", ce);
		ona[ce]=true;
		ce = af[get<0>(ed[ce])];
	}
	ce=bf[1];
	while(ce != -1){
		onb[ce]=true;
		ce = bf[get<0>(ed[ce])];
	}
	int ans=an[n] + bn[1];
	for(int i=0;i<m;i++){
		auto [a,b,c,d]=ed[i]; // a --> b now b-->a
		// if on the shortest path of 1->n or n->1, rerun the dijkstra without the edge, at most 2*n.
		int ab=0,ba=0;
		if(ona[i] or onb[i]){
			ab=dijk(1, i, al).f[n], ba=dijk(n, i, al).f[1];
			printf("on a or b ab %lld, ba %lld\n", ab, ba);
			ans=min(ans, ba+ab);
		}
		else {
			// we (force to go through b->a, without travelling on a->b) or (dont go through b->a :then its just an[n] or bn[1]).
			if (af[b] == i){
				auto [nn, _] = dijk(1, i, al);
				ab+=nn[b];
			}
			else ab+=an[b];
			if (btf[a] == i){
				auto [nn, _] = dijk(n, i, tal);
				ab += nn[a];
			}
			else ab+=bt[a];
			
			if (bf[b] == i){
				auto [nn, _] = dijk(n, i, al);
				ba += nn[b];
			}
			else ba += bn[b];
			if(atf[a] == i){
				auto [nn, _] = dijk(1, i, tal);
				ba += nn[a];
			}
			else ba += at[a];
			ans=min({ans, an[n] + bn[1], ab+ba+c});
			printf("not on a or b, ab %lld, ba %lld\n",ab,ba);
		}
	}
	
	cout<<(ans > 1e14? -1 : ans);
}
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