Submission #1016369

#	Time	Username	Problem	Language	Result	Execution time	Memory
1016369		sun2305	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	343 ms	34748 KiB

commuter_pass

#include <bits/stdc++.h>
#define ll long long
#define se second
#define fi first
#define pll pair<ll,ll>
#define maxn 100005
#define task "XEBUYT"

using namespace std;


const ll inf=1e18;
ll n,m,s,t,u,v,du[maxn],dv[maxn],ans,ds[maxn],dp[3][maxn];
bool vs[maxn];
vector<pll> g[maxn];

void djk1(ll st,ll d[]){
  priority_queue<pll> q;
  fill(vs,vs+maxn,false);

  q.push({0,st});
  while(!q.empty()){
    ll node,w;
    tie(w,node)=q.top();
    q.pop();
    if(!vs[node]){
      vs[node]=true;
      d[node]=-w;
      for(pll it:g[node]) q.push({w-it.se,it.fi});
    }
  }
}

void djk2(ll st, ll ed){
  priority_queue<pair<ll,pll>> q;
  fill(vs,vs+maxn,false);
  fill(dp[0], dp[0] + 100001, LLONG_MAX / 2);
  fill(dp[1], dp[1] + 100001, LLONG_MAX / 2);

  dp[0][0]=dp[1][0]= inf;
  q.push({0,{st,0}});

  while(!q.empty()){
    ll w,node,par;pll p;
    tie(w,p)=q.top();
    tie(node,par)=p;
    q.pop();
    if(!vs[node]){
      vs[node]=true;
      ds[node]=-w;

      dp[0][node]=min(du[node],dp[0][par]);
      dp[1][node]=min(dv[node],dp[1][par]);

      for(pll it:g[node]) q.push({w-it.se,{it.fi,node}});
    }

    else if(-w==ds[node] and min(dp[0][par],du[node])+min(dv[node],dp[1][par])<=dp[1][node]+dp[0][node]){
      dp[0][node]=min(dp[0][par],du[node]);
      dp[1][node]=min(dv[node],dp[1][par]);
    }
  }

  ans=min(ans,dp[0][ed]+dp[1][ed]);
}
int main()
{
  ios_base::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);
  if(fopen(task".INP","r")){
    freopen(task".INP","r",stdin);
    freopen(task".OUT","w",stdout);
  }
  cin>>n>>m>>s>>t>>u>>v;
  for(long i=0;i<m;i++){
    ll a,b,c;
    cin>>a>>b>>c;
    g[a].push_back({b,c});
    g[b].push_back({a,c});
  }
  djk1(u,du); djk1(v,dv);
  ans=du[v];
  djk2(s,t); djk2(t,s);
  cout<<ans;
    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:71:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |     freopen(task".INP","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:72:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   72 |     freopen(task".OUT","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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